A SIM-only deal is a mobile phone contract where you pay a standard monthly fee for your data, calls and texts, but don't pay out for the cost of your phone each month on top.
With the single biggest factor affecting the cost of phone contracts being paying off for the handset itself, it's no surprise that SIM-only plans are considerably cheaper.
If you're looking for a massive data allowance on a SIM-only plan, Smarty (which uses Three Mobile's network), is offering unlimited data for just £18.
The rolling one-month usually costs £20 but will be reduced over 12 months, but the offer ends on 30 July.
So, if you've already got a decent phone that you're happy with, we've rounded up the very best SIM-only deals below for this month.
Top SIM-only deals for July
Best SIM-only deals with huge data
There are several great sim-only deals offering lots of data, some of the best right now come courtesy of EE, Vodafone and ID Mobile.
Giffgaff is also offering 80GB data for £20 a month tariff, the bundle also includes unlimited calls and texts.
EE is also currently offering an incredible 80GB data 18-month plan for £20, which also comes with six months free access to Apple Music, Britbox or MTV Play.
ID Mobile is also offering a great value bundle, with customers able to get unlimited data, minutes and texts for £20 a month.
Best value SIM only deals on each network
From bonus data deals to cheapest monthly cost, there's plenty of other options in the SIM free market right now.
A place where mobile phone users can compare all the networks to find the cheapest deal and spot add-ons and extra freebies included in selected plans.
While Tesco doesn't offer much in terms of add-on extras, opting instead to award families that add more than one contract on their account. In this case, you can get up to 200 bonus Clubcard points, up to £2 off your bill or up to 500 extra minutes.
Like O2 and EE, Vodafone customers can use the VeryMe app to claim weekly perks and rewards such as free coffee and cheap theatre tickets.
EE network claim to give customers triple-speed Internet with all their data plans. You'll also get three months free access to the BT sport app.
Phone users with O2 SIM only contracts can download the Priority app to take advantage of all of its freebies and discounts, including early access to music and festival tickets, free coffee and discounted cinema tickets.
Three are the only UK network to offer unlimited data plans, so the deal below is perfect for those who rely on phone data to stay connected. Customers also get access to perks and discounts with the phone provider's Wuntu platform too.
Text to switch - changing to SIM-only
Switching your mobile phone provider just got even easier, as you can now ditch expensive phone plans with a simple text.
Ofcom regulators have brought in the new rules, which now means anyone wanting to switch - and keep their number - will be able to do so by sending a free message to their network.
Step by step guide if you want to text to switch:
- Consumers text “PAC” for free to 65075
- Consumers receive their PAC code within as little as a minute, plus account details to share with their new provider
Within a working day, consumers’ old service ends and new one begins
Who do I contact if I want to keep my number?
If you would like to keep your existing number you'll need a PAC code from your current phone provider so your number can get ported over to your new provider.
Each code is normally valid for a month. You can even text SWITCH to 65075 from your phone and you will instantly receive a reply message with the code.
If you'd rather speak to someone, here are the numbers to call for all the major network providers: