Cancelling a direct debit on someone else's account
 

So my mobile contract DD is on my GF's account, as i didn't have an account at the time. If i cancel the direct debit, in my name on her account, will it affect her credit rating?

By GF's account, do you mean bank account?

who signed the vodafone contract? are you resetting up the account? if your moving it to yours then theres no problem.

It sounds like you're expecting a negative impact - are you planning to cancel the DD whilst the phone is still in contract and not set up a new payment ? If you do that, then yes it will affect her credit.

as long as you pay until the end of contract, they won't care where the money comes from.