Sort it out

I had a contrat with telkom, that came to an end in April, I went to telkom shelly beach where I canceled my contract, left the country for 6 months, to my surprise I came back to a bill of 950,called the call center spoke to a Mr A Frederick at the retention department, he told me there is no cancelation on my contract. It's the second time Telkom is taking money off my account *******y