If you have been refused handset contracts due to bad credit, you could be accepted as a SIM Only customer instead.

The cheapest contracts only require a minimal credit score and can be a good way to improve your credit rating over time.

Pay-as-you-go (PAYG) SIMs don’t require a credit check, and neither do most short-term 30-day contracts.

If you’re signing up for a longer term contract, say six or 12 months, it’s likely you’ll be put through a credit check.

A contract that includes a handset will demand a higher credit score than a SIM Only deal.

When your contract term expires you will ‘roll-over’ to a monthly subscription.

You’ll be paying the same amount each month, but you’re out of contract so you can leave at any time. You’ll need to give your provider 30 days notice before leaving, so it’s best to plan a switch ahead of time.

If your contract included a phone, rolling over means you’ll keep paying for it when you don’t have to. Switching to SIM-only when your old contract ends lets you keep your old phone and pay less money each month. You can even keep your old number.

How much data you need really depends on how you use your phone when you’re out and about, but a data allowance between 2GB and 4GB is suitable for the majority of people.

Downloading apps, watching YouTube and using Skype or Facetime will eat through your data pretty quickly.

If you save these tasks for when your phone has a WiFi connection, your data usage will be significantly reduced.

Automatic updates are also something to watch out for. Your phone can download large files without warning when it automatically keeps apps and the operating system up to date. If you’re not careful, these updates can take up a sizeable chunk of your data.

Depending on your phone, you may be able to tweak the data usage of specific apps to make sure large files are only downloaded when you’re connected to WiFi.

The size of SIM card you need depends entirely on your phone.

Very few modern phones use the standard size, so you’re probably going to need a micro or nano SIM. If you know the make and model of your phone, a quick Google search should tell you what size you need.

If you do have the wrong size SIM, there’s no need to fret.

A SIM that’s too small will fit into a bigger socket with the use of an inexpensive adapter (these can cost as little as £1).

A SIM that’s too big can be fixed with a pair of scissors by simply cutting away the extra plastic. If you’re confident, you can trim a SIM card down yourself by using instructions and templates which can be found online.

Otherwise, take your SIM card to your local phone shop where a professional can cut it down for you.