Bad service

Ive cancelled a contract dated back to 30 November 2020. Contract end date was 03 Jan 21. I send through 8 emails to retentions to cancel my contract spoke to a consultant last month in Feb , he confirmed a credit to my account and as of today I still have that contract on my name , still paying for the contract What more do I need to do to cancel the contract , phoned 135 today waited for 40 min to be assisted and got cut off