Among the four big networks' own SIM-only plans, 20GB of data costs anywhere from R 99 to R 519 a month. That's a five-fold spread for the same amount of data.
No network is simply overcharging. It's the same 20GB, sold with different things attached. Once you know what those things are, the cheapest plan for you is usually easy to spot.
We re-checked 42 SIM-only plans from Vodacom, MTN, Cell C and Telkom Mobile against each network's own site on 21 September 2026, and every price below is as published that day. We left out four MTN contract plans whose current prices we couldn't confirm.
Same 20GB, five prices
| Plan | Contract | Calls | Price |
|---|---|---|---|
| Vodacom 20GB Data SIM | 24 months | None | R 99 |
| Vodacom PowerFlex 20GB | None | Not stated | R 229 |
| Telkom Mobile-Data 20GB | None | None | R 299 |
| Vodacom PowerFlex 20GB + 300 minutes | None | 300 min | R 299 |
| MTN SuperFlex 20GB | None | Unlimited | R 519 |
Three things account for almost all of that spread: whether you commit to a contract, whether calls are included, and how far up the network's price ladder you buy. Here they are one at a time.
1. A contract buys the cheapest data, but not on every network
Here is every data-only plan we checked, ranked by what a gigabyte of anytime data costs:
| Plan | Contract | Price | Per GB |
|---|---|---|---|
| Vodacom 100GB Data SIM | 24 months | R 229 | R 2,29 |
| Vodacom 60GB Data SIM | 24 months | R 179 | R 2,98 |
| Cell C SmartData "200GB" (100GB anytime) | 24 months | R 349 | R 3,49 |
| Vodacom 20GB Data SIM | 24 months | R 99 | R 4,95 |
| Cell C SmartData "90GB" (50GB anytime) | 24 months | R 279 | R 5,58 |
| Cell C SmartData "50GB" (30GB anytime) | 24 months | R 219 | R 7,30 |
| Telkom Mobile-Data 80GB | None | R 639 | R 7,99 |
| Telkom Mobile-Data 50GB | None | R 529 | R 10,58 |
| Telkom Mobile-Data 10GB | None | R 149 | R 14,90 |
| Telkom Mobile-Data 20GB | None | R 299 | R 14,95 |
| Telkom Mobile-Data 7GB | None | R 109 | R 15,57 |
| Cell C SmartData "20GB" (10GB anytime) | 24 months | R 169 | R 16,90 |
| Telkom Mobile-Data 4GB | None | R 85 | R 21,25 |
| Cell C SmartData "10GB" (5GB anytime) | 24 months | R 109 | R 21,80 |
| Telkom Mobile-Data 2GB | None | R 65 | R 32,50 |
A note on the Cell C rows. Cell C names its SmartData plans after anytime and night data added together, and the night data only works between midnight and 05:00. The table counts anytime data only, which is the figure in brackets. It's also why Cell C's "20GB" plan doesn't appear in the 20GB comparison above.
The six cheapest plans per gigabyte all need a 24-month contract. The cheapest one you can walk away from at the end of any month is Telkom's 80GB, at roughly three and a half times Vodacom's 100GB per gigabyte.
That discount comes with a real commitment. Vodacom's 100GB Data SIM is R 5 496 over its 24 months, and Vodacom's listing is explicit that it's a SIM "that can be used for data only, no calls!"
On Telkom, though, the contract buys you nothing. Telkom's own listing prices every Mobile-Data plan identically on month-to-month and on 24 months: 20GB is R 299 either way. There's no price reason to sign for two years.
2. Calls are where the price climbs
Vodacom sells two PowerFlex plans side by side that make this easy to see. It lists one as "20GB data - R229PM" and the other as "20GB data + 300 minutes - R299PM". The only difference Vodacom states between them is those 300 minutes, and they cost R 70 a month.
At the far end is MTN's SuperFlex. MTN's page says "Enjoy FREE unlimited voice and SMS" and "No contracts, no credit checks. Cancel anytime." Of everything we checked, it's the only month-to-month plan with unlimited calls:
| MTN SuperFlex | Price |
|---|---|
| 5GB | R 209 |
| 10GB | R 329 |
| 15GB | R 429 |
| 20GB | R 519 |
If you phone a lot, that can be the cheapest option you have. If most of your calls are already WhatsApp calls, you're paying for minutes you won't use, and a data-only plan will stretch your money much further.
3. The next tier up is often a better deal than it looks
Networks don't price extra data evenly, and the step up is often cheap:
- Vodacom PowerFlex with 300 minutes: 10GB is R 249 and 20GB is R 299. Twice the data for R 50 more.
- MTN SuperFlex: each extra 5GB costs a little less than the last. It's R 120 from 5GB to 10GB, R 100 from 10GB to 15GB and R 90 from 15GB to 20GB.
- Telkom Mobile-Data: going from 20GB to 50GB adds 30GB for R 230, about R 7,67 a gigabyte against R 14,95 on the 20GB plan itself.
It isn't universal. Telkom's 20GB plan works out very slightly dearer per gigabyte than its 10GB plan. So work it out rather than assume. But if you regularly run out near the end of the month, price the next tier before you buy top-ups.
"Uncapped" versus capped at the same price
Telkom offers two quite different plans at exactly R 529 a month:
- Infinite: 15GB at full speed, then unlimited data at up to 1.5Mbps. Also 300 all-network minutes, plus unlimited Telkom-to-Telkom minutes and SMS.
- Mobile-Data 50GB: 50GB at full speed, and no calls.
"Uncapped" here means a guaranteed floor, not unlimited full-speed data. If you use more than 15GB a month at full speed and don't need the minutes, the capped plan gives you more for the same money. Telkom's bigger Infinite plans raise the full-speed allowance: Infinite Max is 30GB then up to 1.5Mbps for R 699, and Infinite Max Plus is 60GB then up to 5Mbps for R 1 229.
Before you pick a SIM-only plan
- Decide whether you need calls first. It's the biggest single driver of price at any data size.
- Compare anytime data per gigabyte, not the number in the plan's name.
- Check whether the contract actually gets you a discount. On Vodacom's data SIMs and Cell C's SmartData it does. On Telkom's Mobile-Data it doesn't.
- Price the next tier up before you settle on a smaller plan and top-ups.
- Check rollover. Telkom's Mobile-Data keeps unused data until the end of the following month, and Vodacom says every PowerFlex plan includes rollover. Not every listing says either way.
If you're also paying off a phone, SIM-only is only half the picture. Our earlier piece on why the cheapest monthly contract is rarely the cheapest contract covers the handset side.
Compare SIM-only plans on Vulo →
Sources. Prices and terms checked on 21 September 2026 against each network's own site: Vodacom's PowerFlex and SIM-only deals pages, MTN's SuperFlex page and plan data, Cell C's SIM-only catalogue, and Telkom's catalogue (7 September to 6 October 2026 edition) and Mobile-Data listing. Prices change, so confirm on the network's own page before you sign.
Frequently asked questions
- What is the cheapest data per GB on a SIM-only plan in South Africa?
- Of the plans we checked on 21 September 2026, Vodacom's 100GB Data SIM at R 229 a month, which works out to about R 2,29 per GB. It needs a 24-month contract and can't make calls. The cheapest month-to-month data-only plan per GB was Telkom's Mobile-Data 80GB at R 639, about R 7,99 per GB.
- Is a 24-month SIM-only contract cheaper than month-to-month?
- Per gigabyte, usually. The six cheapest data-only plans per GB that we checked all need a 24-month contract. It doesn't hold everywhere, though. Telkom lists its Mobile-Data plans at the same price on month-to-month and on 24 months, so locking in there saves nothing.
- Which SIM-only plan has unlimited calls without a contract?
- Of the plans we checked, MTN's SuperFlex, from R 209 a month with 5GB. MTN's page says "No contracts, no credit checks. Cancel anytime" and "Enjoy FREE unlimited voice and SMS".
- Is uncapped SIM-only data really unlimited?
- Not at full speed. Telkom's Infinite plan gives 15GB at full speed and then unlimited data at up to 1.5Mbps, for R 529 a month. The same R 529 buys Telkom's Mobile-Data 50GB: 50GB at full speed, with no calls.
- Does unused data roll over on SIM-only plans?
- On some. Telkom's Mobile-Data plans keep unused data until the end of the following month, and Vodacom says all its PowerFlex plans include rollover data. Not every listing states it either way, so check the specific plan.
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