Earlier termination of the contract due to poor service provided

Hello customer service, I have contracted DSL (Kundennummer DE16462525) but from the begging my speed wasn't higher than 0.2 MB (contracted 16MB). I have contacted customer service for 3 times but no solution was given. I had no other choice but to go for a new provider but now Im told that O2 can only release my contract by the end of May. As both my wife and myself, we work from home, we have a huge problem for not being able to have internet access. My question is can O2 terminate the contract as soon as possible as the contracted service is not being provided or can O2 provide a solution until the end of May when it will be moved to another company? Thank you