Change tariff

[Tyriq]

I want to change tariff using the money in top up it

[pgn]

Your MyO2 should let you swap tariff, @Tyriq - but you have posted in Pay Monthly (Contract) yet mention top-up - which type of SIM are you using?

You can contact O2 on any of the ways in here for more help, @Tyriq 

Guide: How to find help & contact O2 and this is the PAYG top-up guide: Guide How to Top Up (PAYG)