EXTREMELY POOR SERVICE FROM MTN SA

I upgraded my phone in January and my experience was very smooth until I decided to downgrade my sim-only package to a cheaper one. I was sent from pillar to post for a good 2 months. I then decided to cancel my sim only contract with MTN and I even received a cancellation confirmation but to my surprise I still got billed for the same sim I cancelled. When I call the call centre to inquire about this again i got sent from pillar to post. Extremely horrible service from MTN. When upgrading they are quick to assist but downgrade and cancellation they will work at a snails pace and still charge you more.