Retrieve bill / get refund

Hello, could soumeone help me redeem a router return bill?

I got a receipt some months after the premature termination of my O2 DSL Contract due to moving abroad. I understand that this is because I till haven’t sent my router, which I intend to do. But I would need support in the following matters:

1. The online bill says I can check it in MeinO2. In fact I can’t, because there is no longer an account associated with my data. In this case, kindly help me get this access or just receive my full bill in PDF via e-mail.

   

    

2. I was informed on how and when to send back the router by O2 customer support, I even got a form to send it back, but I wasn’t notified of any deadline. Being abroad, I planned to send back the router in a few weeks when I visit Germany. Having received bill which leaves me no choice, but to do it immediately. In this case, I need help retrieving the bill. The bill is due on Feb 25 and I plan to send back the router tomorrow, so it seems like there is time to redeem it. Please let me know which are the options to retrieve it/get a refund in the case I am charged. It would be very helpful!

Thank you in advance,

Kristi