Cheap Postpaid Mobile Plans Under $20
In our database, we're comparing 10 postpaid mobile plans priced at $20 a month or less from 8 providers across
the Optus, Telstra and TPG networks (TPG's network also covers Vodafone-branded plans). Prices run from $12 to $20
a month, averaging $17.00, with data allowances from 10GB up to 100GB. This list has narrowed sharply since our
last update -- only 2 of the 10 plans stay genuinely $20-or-under long-term this time, and both
are data-only SIMs. The other 8 start below $20 only as a limited-time promo and revert to a
higher regular price afterwards, in some cases nearly triple.
$12.00
Cheapest advertised price
(Coles Mobile, promo)
$20.00
Cheapest regular price
(tied: Vodafone & Belong)
2 / 10
Plans genuinely $20-or-under long-term
Best value, genuinely under $20: Vodafone's Small Data SIM Only Plan is still the
standout at $0.33/GB (60GB for $20/month, data-only, TPG network, 5G-capable). The only other plan
that stays genuinely under $20 long-term is Belong's 20GB Mobile Broadband at
$1.00/GB (Telstra, data-only, 5G-capable). Both are data-only -- there's currently no plan with
unlimited talk & text in our database that stays under $20 without a promo.
Read the fine print: "under $20" is doing a lot of work on this page. Most plans below only cost
under $20 for an introductory period (often 3-6 months) and then jump to a higher regular price -- in some cases
nearly triple. Where that applies, we show both the current price and the regular price it reverts to. Always
check the plan's terms and confirm the ongoing cost with the carrier before signing up.
Genuinely $20-or-under, no price hike (2 plans)
Sorted by cost per GB (regular price), lowest first. These plans cost the same now as they will on renewal -- what you see is what you keep paying.
| Provider | Plan | Network | Data | Talk & Text | Price | Cost / GB | |
|---|
| Vodafone | Small Data SIM Only Plan |
TPG |
60GB (4G,5G) | N/A | $20.00 / 30 days | $0.33 |
Visit site |
| Belong | 20GB Mobile Broadband |
Telstra |
20GB (4G,5G) | N/A | $20.00 / 30 days | $1.00 |
Visit site |
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 | Network | Data | Talk & Text | Now | Then (regular) | |
|---|
| Coles Mobile | Coles 45GB Month to Month Mobile Plan |
Optus |
75GB (4G,5G) | Unlimited | $12.00 | $35.00 |
Visit site |
| Dodo | $30 Unlimited Mobile Plan |
Optus |
40GB (4G) | Unlimited | $15.00 | $30.00 |
Visit site |
| Flip | 10GB Mobile Plan |
Optus |
10GB (4G) | Unlimited | $15.00 | $24.90 |
Visit site |
| SpinTel | 25GB SIM Only Mobile Plan |
Optus |
25GB (4G,5G) | Unlimited | $15.00 | $23.00 |
Visit site |
| Tangerine Telecom | 30GB 4G Mobile SIM |
Telstra |
60GB (4G) | Unlimited | $15.00 | $30.00 |
Visit site |
| Tangerine Telecom | 50GB 5G Mobile SIM |
Telstra |
100GB (4G,5G) | Unlimited | $18.00 | $38.00 |
Visit site |
| Aussie Broadband | Value Mobile Plan |
Optus |
45GB (4G,5G) | Unlimited | $20.00 | $40.00 |
Visit site |
| Dodo | $40 Unlimited Mobile Plan |
Optus |
80GB (4G,5G) | Unlimited | $20.00 | $40.00 |
Visit site |
Compare by network
Optus
Optus network
6 plans under $20 in our database, but none stay under $20 long-term right now.
Cheapest on renewal: SpinTel 25GB SIM Only Mobile Plan at $23.00.
Telstra
Telstra network
3 plans under $20 in our database, from $15.00 (Tangerine Telecom, promo) or $20.00 with no promo trap (Belong).
Best value: Belong 20GB Mobile Broadband at $1.00/GB.
TPG
TPG network
Just 1 plan under $20 in our database right now (also covers Vodafone-branded plans).
Best value: Vodafone Small Data SIM Only Plan at $0.33/GB -- also genuinely under $20 long-term.
Genuinely $20-or-under, by network speed
Only the 2 plans that stay $20-or-under long-term (no promo price hike) qualify here, and both happen to be 5G-capable. There's currently no 4G-only plan in our database that stays genuinely under $20 -- the providers that used to fill that spot (Cmobile, AQUA Mobile) don't have any postpaid plans under $20 in this update.
5G-capable (2 plans)
TPG
Vodafone
Small Data SIM Only Plan
$20.00 / 30 days
60GB (4G,5G) · Data only · $0.33/GB
Telstra
Belong
20GB Mobile Broadband
$20.00 / 30 days
20GB (4G,5G) · Data only · $1.00/GB
Frequently asked questions
What is the cheapest postpaid plan under $20 in your database?
In our database, the cheapest plan by advertised price is Coles Mobile's 45GB Month to Month Mobile Plan at $12.00/month (Optus network), though that's a promotional price that reverts to $35.00. Looking at regular/ongoing prices instead, the cheapest plans that stay under $20 long-term are Vodafone's Small Data SIM Only Plan and Belong's 20GB Mobile Broadband, both at $20.00/month.
Which under-$20 plan is the best value per GB?
In our database, Vodafone's Small Data SIM Only Plan works out to just $0.33 per GB (60GB for $20/month, data-only, TPG network). Belong's 20GB Mobile Broadband is the only other plan that stays genuinely under $20, at $1.00/GB.
Are all these plans genuinely under $20 long-term?
No. In our database, only 2 of the 10 plans are genuinely $20 or under with no price increase -- Vodafone's Small Data SIM Only Plan and Belong's 20GB Mobile Broadband. The other 8 start below $20 only as an introductory promo price and revert to a higher regular price later, in some cases nearly triple, once the promo period ends.
Is there a plan under $20 with unlimited talk and text that isn't a promo?
Not currently in our database. Both plans that stay genuinely under $20 long-term are data-only SIMs with no talk or text included. If you need calls and texts, the cheapest options right now are promotional prices that increase later -- see the "starts under $20" table above for details.
Which network has the most postpaid plans under $20?
In our database, Optus has the most with 6 of the 10 plans, followed by Telstra with 3 and TPG with 1. None of the current Optus plans stay under $20 long-term without a promo -- the cheapest Optus plan on renewal is SpinTel's 25GB SIM Only Mobile Plan at $23.00.
What's the plan with the most data under $20?
In our database, Tangerine Telecom's 50GB 5G Mobile SIM offers the most data at 100GB for a promotional price of $18/month, though its regular price is $38/month after the promo ends. Among plans that stay $20 or under long-term, Vodafone's Small Data SIM Only Plan offers the most data at 60GB.
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. 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 and all plan information directly with the carrier before signing up.