Insurance cancelled on 18/05/2017 still being billed to date

I have contacted Telkom from the 21/07/2017 to date. I have logged numerous cases. Spoke to so many consultants. Finrite has confirmed that the insurance was cancelled on the 18/05/2017. Telkom says they have not received notification. I have now cancelled the phone contract and still no response. Please advise on how I can get my refund as well as take Telkom up on this.