Alternative way to pay the mobile service fee?

Hello, recently I have moved abroad, so I aborted my subscription to the O2 mobile service. However, it seems like there is still some remaining fee to be paid. The problem is that I already closed the German bank account (my mobile fee had been transferred to O2 from this bank account) and I still need some time to open a new bank account in the country I have moved to. Is there any alternative way of paying the fee? Thank you very much!