@CGS
No new sim required and yes you keep your credit.
You can change tariff in your MyO2 http://www.o2.co.uk/myo2 but you won't be able to switch back to basic PAYG if you switch.
I have no affiliation whatsoever with O2 or any subsidiary companies. Comments posted are entirely of my own opinion. This is not Customer Service so we are unable to help with account specific issues.
Please select the post that helped you best and mark as the solution. This helps other members in resolving their issues faster. Thank you.
