hello, I accidentally made a payment to o2 instead of to a friend (I got the IBANs confused)… a dumb mistake, but it happened. 

I have the exact date of the transfer, and the IBAN that the transfer came from. There is no kundenummer with the payment, because it was not intended for o2. who can I contact to refund this transfer?

is there a number of an english customer service hotline? 

any help is appreciated