prolongation of contract

on the 14th of this month my current contract expires. I am currently not in Germany and before November I am not going to be in the city of my residence. I would like to prolong my contract and get a new phone, but the online services for me are not working, while they haven't still recognized that they have made money withdrawal from my bank account.

Is it possible to prolong the SIM contract and later on get a new phone contract (maybe after two weeks), or can I go to any o2 store in Germany (not only in the city of residence) and get all fixed (with getting the phone on spot if available)?

thank you all for any advice you might have.

Cheers!