@mariana.pereira.camargo look at this FAQ.

https://hilfe.o2online.de/english-o2-community-mobile-43/extraordinary-cancellation-because-of-moving-abroad-458522

Hi @mariana.pereira.camargo, 

welcome to our English community.   

I am happy to help you with the cancellation because of moving abroad. @Joe Doe already gave you the instructions about the procedure how to cancel your contract when you move out of Germany.   

Please fill out the following document: extraordinary cancellation because of moving abroad

As you see, we need additionally to your cancellation the following documents: 

• a deregistration certificate of your present place of residence in Germany
• a notification of your new foreign domicile (alternatively a confirmation of your employer or landlord)
• your approval for us to charge the all-inclusive basic fee for 3 months (see cancellation form)

As soon as we have all these documents, we will cancel your contract as soon as possible. 

I hope I could help you with this information. 

If you have any further questions, just feel free to contact us here in our English community. 

Loving greetings,

Tobias