Cheap Mobile Plans Under $20 on the Optus Network
Optus network only -- every plan below runs on Optus infrastructure. Check Optus coverage in your area before signing up.
In our database, we're comparing 14 mobile plans priced at $20 a month or less on the Optus network, from
8 providers -- down from 19 plans and 10 providers on our last update, as AQUA Mobile and E.Tel have both
dropped off this list entirely. Prices run from $1.00 to $20.00 (that $1.00 figure is Yomojo's first-month-only
promo -- more on that below), averaging $13.64, with data allowances from 5GB up to 100GB. Only
2 of the 14 keep their price with no promo increase -- and notably, both of those are now
weekly-billed plans, since AQUA Mobile's two genuine monthly plans are no longer in our database. The other
12 start at a discounted intro price and revert to a higher regular price once the promo
period ends.
$1.00
Cheapest advertised price
(Yomojo, first month only)
$10.00
Cheapest price with no promo hike
(amaysim, 7-day)
2 / 14
Plans genuinely $20-or-under long-term
Best value overall: Coles Mobile's Coles 45GB Month to Month Mobile Plan
works out to $0.16/GB at its $12.00 intro price (75GB, talk & text included) -- it's a
promo, reverting to $35.00 (≈$0.47/GB regular). Yomojo's Starter Prepaid technically beats this on
paper at $0.03/GB, but only for the first month before jumping to $24.00 -- see the warning below. If you
want a price that never changes, amaysim's 7 Day SIM Only Prepaid Plan is now the only
practical genuine option, at $1.00/GB for 10GB every 7 days -- there's currently no plan on this page that
combines a genuine (no-hike) price with monthly billing.
Read the fine print: 12 of the 14 plans below only cost under $20 for an introductory
period and then revert to a higher regular price. The steepest jump by far is Yomojo's Starter Prepaid --
just $1.00 for the first month, then $24.00 from month two, a 24x increase. Always check the ongoing price,
not just the headline number, before signing up.
Genuinely $20-or-under, no price hike (2 plans)
Sorted by cost per GB, lowest first. These plans cost the same now as they will on renewal. Both happen to bill weekly this update -- AQUA Mobile's monthly no-hike plans are no longer in our database.
| Provider | Plan | Data | Talk & Text | Price | Monthly Equivalent | Cost/GB | |
|---|
| amaysim | 7 Day SIM Only Prepaid Mobile Plan |
10GB (4G,5G) | Unlimited |
$10.00 / 7 days |
≈$42.86/mo |
$1.00 |
View plan |
| Optus | Flex Plus - Weekly |
5GB (4G,5G) | Unlimited |
$13.00 / 7 days |
≈$55.71/mo |
$2.60 |
View plan |
Sorted by current advertised price, lowest first. "Now" is the price you'll pay today; "Then" is the regular price it reverts to once the promo period ends.
| Provider | Plan | Data | Talk & Text | Now | Then (regular) | Monthly Equivalent | Cost/GB (now) | |
|---|
| Yomojo | Starter Prepaid |
29GB (4G) | Unlimited |
$1.00 | $24.00 |
$1.00/moRegular $24.00/mo |
$0.03 |
View plan |
| amaysim | 30GB Data Only Prepaid Mobile Plan |
30GB (4G) | N/A |
$10.00 | $25.00 |
≈$10.71/moRegular ≈$26.79/mo |
$0.33 |
View plan |
| amaysim | 15GB Unlimited Small SIM Only Plan |
15GB (4G,5G) | Unlimited |
$11.00 | $30.00 |
≈$11.79/moRegular ≈$32.14/mo |
$0.73 |
View plan |
| Coles Mobile | Coles 45GB Month to Month Mobile Plan |
75GB (4G,5G) | Unlimited |
$12.00 | $35.00 |
$12.00/moRegular $35.00/mo |
$0.16 |
View plan |
| Optus | Flex Plus - 30GB Data |
50GB (4G,5G) | Unlimited |
$14.00 | $40.00 |
$15.00/moRegular ≈$42.86/mo |
$0.28 |
View plan |
| Dodo | $30 Unlimited Mobile Plan |
40GB (4G) | Unlimited |
$15.00 | $30.00 |
$15.00/moRegular $30.00/mo |
$0.38 |
View plan |
| SpinTel | 25GB SIM Only Mobile Plan |
25GB (4G,5G) | Unlimited |
$15.00 | $23.00 |
$15.00/moRegular $23.00/mo |
$0.60 |
View plan |
| Flip | 10GB Mobile Plan |
10GB (4G) | Unlimited |
$15.00 | $24.90 |
$15.00/moRegular $24.90/mo |
$1.50 |
View plan |
| Optus | Flex Plus - 35GB Data |
65GB (4G,5G) | Unlimited |
$17.00 | $49.00 |
≈$18.21/moRegular $52.50/mo |
$0.26 |
View plan |
| amaysim | 100GB Data Only Prepaid Mobile Plan |
100GB (4G,5G) | N/A |
$18.00 | $50.00 |
≈$19.29/moRegular ≈$53.57/mo |
$0.18 |
View plan |
| Dodo | $40 Unlimited Mobile Plan |
80GB (4G,5G) | Unlimited |
$20.00 | $40.00 |
$20.00/moRegular $40.00/mo |
$0.25 |
View plan |
| Aussie Broadband | Value Mobile Plan |
45GB (4G,5G) | Unlimited |
$20.00 | $40.00 |
$20.00/moRegular $40.00/mo |
$0.44 |
View plan |
Two plans in our database are data-only: amaysim's 100GB Data Only Prepaid Mobile Plan ($18.00, promo) and amaysim's 30GB Data Only Prepaid Mobile Plan ($10.00, promo). The other 12 all include unlimited talk & text.
Compare by billing cycle
Billing cycle affects how the sticker price translates to a monthly cost -- shorter cycles look cheap upfront but bill more often.
7-day plans (2)
amaysim's 7 Day SIM Only Prepaid ($10.00, 10GB) and Optus's Flex Plus - Weekly ($13.00, 5GB) -- both genuinely no-promo-hike, but with monthly equivalents of ≈$42.86 and ≈$55.71 respectively. These are currently the only genuine (no-hike) plans on this page.
28-day plans (5)
amaysim's 30GB Data Only ($10.00), 15GB Unlimited Small ($11.00) and 100GB Data Only ($18.00), plus Optus's Flex Plus - 30GB Data ($14.00) and Flex Plus - 35GB Data ($17.00) -- all promo-priced.
30-day plans (7)
Coles Mobile, Dodo (both plans), Flip, SpinTel, Aussie Broadband and Yomojo -- every plan in this group is a promo this update, since AQUA Mobile's two genuine monthly plans are no longer in our database.
Compare by network speed
10 of the 14 plans support 5G; the rest are 4G-only.
5G-capable (10 plans)
From amaysim's 7 Day SIM Only Prepaid ($10.00, genuine) up to amaysim's 100GB Data Only Prepaid ($18.00, promo). Best value: Coles Mobile's 45GB Month to Month Plan at $0.16/GB.
4G only (4 plans)
Yomojo's $1.00 Starter Prepaid, amaysim's 30GB Data Only Prepaid, Dodo's $30 Unlimited, and Flip's 10GB Mobile Plan -- all promo-priced this update. Best reasonable value: amaysim's 30GB Data Only Prepaid at $0.33/GB.
Frequently asked questions
What is the cheapest Optus plan under $20 in your database?
In our database, the cheapest by advertised price is Yomojo's Starter Prepaid at $1.00 for the first month, though that jumps to $24.00 from month two. Excluding that first-month-only offer, amaysim's 30GB Data Only Prepaid Plan is cheapest at $10.00 (data-only). Among plans with no promo hike at all, amaysim's 7 Day SIM Only Prepaid Plan is cheapest at $10.00 every 7 days.
What happened to AQUA Mobile and E.Tel's plans?
As of this update, AQUA Mobile's $15 and $20 Monthly SIM Only Plans and all three of E.Tel's Value plans are no longer listed under $20 on the Optus network in our database. This also means the page has lost its only genuine (no-hike) monthly-billed plans -- if you were relying on one of these, check with the provider directly for their current offering.
Is Yomojo's $1.00 plan actually a good deal?
Not really, if you're planning to stay past month one. In our database, Yomojo's Starter Prepaid is $1.00 for the first month only, then jumps straight to $24.00 from month two -- a 24x increase and the steepest promo cliff of any plan on this page. It's worth considering only if you specifically want a one-month, no-commitment SIM.
Which under-$20 Optus plan is the best value per GB?
In our database, Coles Mobile's Coles 45GB Month to Month Mobile Plan works out to $0.16/GB at its $12.00 intro price (75GB, talk & text included) -- though it's a promo, reverting to $35.00 ($0.47/GB regular). Among plans that keep the same price long-term, amaysim's 7 Day SIM Only Prepaid Plan is best at $1.00/GB -- it's currently the only genuine plan under $20 on this page.
Are all these Optus plans genuinely under $20 long-term?
No. In our database, only 2 of the 14 plans keep their price with no increase: amaysim's 7 Day SIM Only Prepaid Plan and Optus's own Flex Plus - Weekly plan, both billed every 7 days. The other 12 start below $20 as an introductory promo and revert to a higher regular price afterwards -- so always check the ongoing price before signing up.
What's the plan with the most data under $20?
In our database, amaysim's 100GB Data Only Prepaid Mobile Plan offers the most data at 100GB for a promotional price of $18.00/month, though its regular price is $50.00/month after the promo ends. Among plans that keep the same price long-term, amaysim's 7 Day SIM Only Prepaid Plan offers the most data at 10GB.
Prices and data allowances shown are current in our database as of August 2026 and reflect advertised carrier pricing at time of listing. Where a plan has an introductory promo, we show both the current and regular price so you can see the true long-term cost. Monthly-equivalent figures are calculated as price × (30 ÷ billing days) and are provided for comparison purposes only -- they do not represent an actual monthly billing amount for plans that don't bill monthly. Plans, prices and inclusions change frequently, and details are entered into our database manually so errors are possible -- we do not guarantee the accuracy of any price, allowance, or other detail shown. Always confirm the final price, billing cycle, and all plan information directly with the carrier before signing up.