2G SIM obsolete - what to do next

[Norman44]

I have an old Nokia 105 'feature' phone (i.e. not a smartphone) that only works on 2G. I have a (mini) SIM that currently works with O2 on PAYG, but I've received a text to say the SIM is obsolete and will have to be changed. My assumption is that although 2G is continuing, it won't be available for customers, so the 2G-only phone is soon going to be useless.

I want to keep my number, but use it with a new 5G SIM on a new smartphone (which I'll buy SIM-free online) on a different network with a SIM only deal..

I'd like to keep my contacts list from the old SIM and the phone, if possible.

I went to the local O2 shop. The person I spoke to did not seem to be an expert. They said they could put a new SIM in the Nokia 105, but it might not work, and going back to the original one wouldn't then be possible, so I didn't risk it.

I assume the mini SIM won't fit the new phone. I assume I'll get a new SIM when I buy the deal, but how do I get the old phone number into it?

I'm new to all this and would like advice on what order to do things in.
Thanks.

[Enlli]

As your phone is 2G it should work for some time yet. It is 3G that is being closed down first 

The Nokia 105 gave the option to save contacts to the SIM or the phone and transfer between the two. Once contacts are on the phone you could simply get a replacement SIM if you call in with photo ID. Replacement SIM cards are backwards compatible so they will fit

[MI5]

@Norman44 

To get your old number on a new sim you need to ask O2 to do a number migration.

Guide: Migration & porting into O2 

Guide: How to find help & contact O2