Sim cards are required for all mobile phones no matter how basic they are or how technologically advanced they are.
Sometimes sim cards need replacing (damaged) or sometimes you want to change your number (you are allowed one free number change from O2) or your tariff (a lot of tariffs can be changed without changing your sim) or you buy a new phone and need a different sim.
If you get a sim instore or order one online, if you want to keep your number, but it is not a blank sim (blank sims will have replacement written on them) then you need to complete this form: http://swapmysim.o2.co.uk/
After completing the online sim swap form you must wait approximately 24 hours for the sim swap process to complete. You will know when the sim swap process is complete as you will lose your signal. Sometimes turning the phone on and off and taking the sim out 'may' speed up this process. If it is a blank sim then this means that there is no number attached to the sim, however you still need to complete the sim swap form online to get your number transferred to the new sim.
As 4G are the newest sims, they are the ones which are generally handed out to customers who request them, even if you are not on 4G. 4G sims can be used in 3G phones and on a 3G tariff, but you can't use a 3G sim for a 4G tariff.
There are 3 different size sims available:
-Standard sized sim (usually comes as a combined sim even when you just want a standard sim - a combined sim will still work in a standard size sim phone).
-Micro sim - about half the size of a standard sim - required for iPhone 4.
-Nano sim - about half the size of a micro sim - required for iPhone 5 and iPhone 5s.
At the moment there are no options to have a sim which can convert between all 3 types of sims. Although the micro is currently combined with the standard sim and the nano sim is currently combined with the standard sim. If you have been using a micro sim or a nano sim and you have a new phone which fits a standard sim then you can use an adapter (usually black plastic). However, I am currently unaware of there being an adapter to convert from nano to micro and vice versa.
New sims can be ordered from here:
https://www.o2.co.uk/freesim/
Although all members on here would like to help, we are all customers and therefore we cannot access any account information on anybody. Therefore if you have any problems with the sim swap process (if you have waited over 24 hours) then I suggest that you should contact O2 customer services to confirm that they have received your request and to find out why it hasn't completed yet. Please bear in mind that during busy periods (bank holidays, Christmas period) or during bad weather, the sim swap process may take longer than 24 hours.
I apologise for making this information primarily about PAYG and other general information, however as I am not a Pay Monthly customer I do not feel that I could give out information as I am not 100% sure about their process for replacing sim cards and I want this information to be helpful.
