When I went in a couple of months ago to do the same thing (_slightly_ more complicated situation - I had two accounts but only one SIM card and had topped up t

When I went in a couple of months ago to do the same thing (_slightly_ more complicated situation - I had two accounts but only one SIM card and had topped up the wrong account), the store manager told me he couldn't help me and handed me their store phone dialled to their call centre (!). The man on the other end of the phone was totally unable to solve my problem and in the end just gave me £10 of free credit on the account I'd meant to top up. He didn't ask for any ID or verification at any point, except for the serial number on the SIM card. It was a pretty bizarre customer service experience.