Very poor service and no regard for customers

I am very unhappy with the service I have received from Telkom. I have not received any assistance from them regarding the cancellation of my data sim. When I took it I was told that I am able to cancel it anytime when I do not need it anymore... I called them requesting that they cancel the sim and I told that I need to complete their cancellation form which I did and it through to them. Till to date they have not cancelled it and I am told that I owe the R1900 now. This is very unacceptable as I provided them with all necessary documentation to have them cancel it. They have a poor service and have no regard for customers at all.