Incorrect Billing

Good Day

I would like to be assisted with my MTN account,my account is forever legal because of incorrect billing. My contract ended Feb2021 then i was put on month to month without my consent ,i later phoned in to cancel. However, since I cancelled I am being charged R173.91 for a device which I don't understand what it is for since my contrac***** been a good 15 month with hope that the billing will be rectified but is not. The only contract that i am liable for is the R526.00

This is affecting my account negatively,every month I am hoping this will be sorted but is not. Currently my lines are blocked and I am being sent from pillar to post.