Netstar is a useless company

Netstar suck big time. I emailed, phoned and eventually after many complaints I received a cancelation letter from Kutlwano from Netstar. I am still receiving calls from them to pay for a service which has been canceled already! I am being harassed by their collections department to pay, pay for something that has been canceled. I have emailed Hybrid collections the cancelation letter today 16/07/2025. I am seriously considering taking this further. The car has been sold 4 months ago and this is how long it take for a useless company to cancel a contract. I am still getting calls from Netstar to say the contract is active on their side, how is this possible if I received a cancelation letter????