Poor service

I have used the service/router for a month and I wasn't happy with the service and I went to the shop in Maponya for an upgrade and they told me my area doesn't cover 5G. I cancelled the service and returned the router at Maponya. They made me signed the form and asked me to called Mnt to cancel. When I called cancellation department they said Maponya must cancel it. And we had a group call among us, Mtn call centre, myself and Mtn Maponya and I was assured it will be cancelled. It's been 2 months and they keep deducting the month. Kindly do your job and cancel the service as I don't have router on my side