MTN - frustration

I returned the MTM Home Ultra device in June 2024, but I'm still getting billed for it. Please cancel this billing and refund me the incorrect months billed, immediately, or I'm going to move my accounts to Vodacom. I tried to phone them, but either they didn't answer the call, or they told me to go to the branch, which is in Ballito. I stay in Johannesburg.