Poor service

I have been trying to close my contract with you since February as it was coming to an end... I went to the southgate branch and they said I have to wait for the day it ends to cancel it, and I did, I called your call centre and they said I should go to the branch, at the branch they said they only starting the process of cancelation. but now I'm being charged for a month to month and I did specifically say I don't want a month to month cos my Sim card has been lost for a long time. And I don't understand why I'm being charged for a month to month when the contract was only for 36 months and the 36 months has finished. And when I was offered an upgrade I did say I don't want to continue with you guys cos I no longer have that number