Did you also buy a smartphone via o2? The monthly installments are debited separately under a different number.

Thanks, I didn't think about that, I guess it was because last month's invoice for the monthly tariff came with some other charges and I thought it had the phone monthly installment there, but it didn't.

Hallo @hfigueiredo ,

the invoice for your mobile contract that you got last month was the first one for that tariff, which is why you had an additional fee on that one. Aside from that stefanniehaus had the correct guess, as the 40€ belong to the monthly installments of the smartphone. If you have any further questions please let us know.

Kind regards, Sven