@P.P.M.K 

Have you concluded the contract in the o2 shop?

I have concluded the contract in Saturn

Then you can't revoke.

Oh no, Are there no other options left to cancel it?

You cannot revoke contracts concluded in the store. Ask Saturn whether there is a goodwill policy.

Hello @P.P.M.K ,

welcome to the o2 Community .

I assume that generally you wanted to withdraw from the contract, before it even started. That would be something that you could only talk about with the store that you made the contract at, in this case a Saturn. As Bumer stated this would be entirely good will, as a contract signed in person does not have the normal period of 14 days that one would have to withdraw from the contract if it was done online or by hotline.
A cancellation would end the contract at the end of it’s normal contractual duration, which depending upon what kind of contract you signed would probably be in about 2 years.

Kind regards, Sven