Assistance with cancelling contract

Hello my job recently finished in Germany and I have moved back to England.   I tried to cancel my O2.de contract before I left and was to I would receive a special form via email from O2.de and would have to pay for 4 months.  I am happy with this but have never received the email with the form so had to leave Germany without cancelling properly.  My German bank account is now closed but my 02.de is still active and I am being billed for the mobile service.  Can anyone help me?  My German is not very good and when I call customer support I cannot get anyone to speak English.