I have been charged for two device plans after switch up

[Ally10]

I have been charged for two device plans after switch u

[madasaf1sh]

@Ally10 

It can happen where the billing dates cross, you will need to contact o2, the best way is via Social Media all the details are here Guide: How to find help & contact O2 

[jonsie]

It's possible that you have taken out a new contract rather than using the upgrade button

Ask O2 to migrate your number from the old contract to the new one

That will terminate the original contract

Guide: Migration & porting into O2 

Guide: How to find help & contact O2