Telkom keeps g me on my cancelled account

I have canceled my account in March 2020 in June 2020 I get a sms that I ow them R547.31 My last invoice from Telkom Was in April 2020 stating that I still need to pay R57.31, When I dialed in for support they stated that I still owed +-R280 which i disagree with as when you cancel your account your account needs to be paid in full so I am being charged an for service on an extra month of service when my mobile line was disconnected.