Mobile change

[Bible]

I was thinking of upgrading my phone to a new one do I need to take on a new sim contract 

[pgn · Accepted solution]

No, you can buy a new phone from any source and just swap the SIM into the new handset @Bible 

Guide: Upgrading Your O2 Phone 

This is providing your current Device Plan has been paid-off Guide: How does O2 Refresh work? 

Many find it cheaper to get a new SIMO contract at the same time, uSwitch can be very competitive.

Good luck!