What are the consequences if I cancel my contract?

Dear O2 KundenService

I ordered a dsl connection about 2 weeks ago 

It should've been started from 17th of january 

But there is some issues and my DSL is not working yet

getting service from hotline is a disaster, it taket more than 1 hour to talk to the operator and they can't communicate in english

I'm considering cancellation of my contract

But I want to know what would be the concequenses and would this cancellation be free of charge for me?

If not how is that afterall?

Kind regards,

Mohammad