Unless there is a problem with your existing SIM preventing you from using it from now on, there's no reason to change it. I'm actually quite surprised you've even been sent a new SIM when you've basically just changed your payment plan. There's nothing about a change of plan that, of itself, should mean your SIM needs replacing.
That said, if you are changing to a new SIM for whatever reason, then you can activate it using this EE page.
Ok, I don’t think there is a problem with existing SIM. Is there a way to check if it’s ok. As you can already guess I’m not tech savvy so any help will be wonderful
I'm assuming you're moving to SIM only but keeping your existing phone? If so, just carry on. There's no need to change anything - you're altering your payment plan but otherwise nothing else is changing, so just keep using your phone as normal!!
If you're changing your phone and also moving to SIM-only, then the way to check it's ok is to..... take the SIM out of your current phone and put it in your new phone. If it fits and the new phone works ok, then it's ok 🙂
