It is not possible to terminate a contract early in such cases.

When did you order the new contract? If it was online or by phone and it is not longer than 14 days ago since the contract started you should be able to cancel it. Send an email to widerruf@cc.o2online.de but make it clear that you only want to cancel the contract the for the tarrif and not the phone.

It has only been 10 days yet. I ordered it on 17th of October. 

But if i only cancel the contract. Then How would it function . Can i do that? And how will i pay for the new device then? 

There is a small risk that o2 will only let you cancel the phone and the tarrif at the same time if they were ordered together, but it should work and is your only option to not have to pay for both tarrifs for the next 10 months.

The phone us a separate contract so you would then just pay the monthly installment for the phone and continue to pay for the tarrif you already had.

What exactly do i have to write in the email to do that? 

That you wish to terminate the contract for tarrif xxx with the telefone number xxx, customer number xxx. You can also write explicitly that you only wish to cancel the tarrif and do not wish to cancel the contract for the IPhone.

I also saw that i can transfer the contract to someone. Is it also possjble? 

Hello @Hassan Shabbir,

sorry for the late response.

As bs0 already mentioned, if you have concluded the contract by telephone or online, you have a withdrawal period of 14 days. Unfortunately, this period has been exceeded, so it is no longer possible to terminate the contract. 

However, you can apply for a change of the contract holder. You can find further information on this under the following link: 

Best regards
Cora