Termination of contract

About a month ago I had sent my request for termination of my O2 contract by post but it got sent to the wrong address so I did not get my termination confirmation. Last Tuesday, my termination letter was received. I called the customer service to ask them and they said they have received my letter. However I haven't received any confirmation either by email or post saying that they will be terminating my contract. My contract is a flexible contract and I just need to inform them about 1 month before I want to end it. I also returned my Rooter with the DHL Retoure but I didn't get any confirmation for that either. Could someone help me with the same? How long should I wait until I get a confirmation. I also want to know if O2 has received my Rooter as well as my termination letter since it's been a long time with no response from the other side. Thanks a lot for the help!