Internet disconnectivity due to a contract change

Hello,

The previous tenant transferred his contract to me, and I accepted the offer yesterday via the o2 website. 

Then the internet connection in my apartment immediately went down. I need it for work, so I'm wondering how long it will take until I can use the internet in my apartment again?

Please help me, I can't believe that changing the name on the contract online would interrupt the internet connection.

Thank you!