MTN double billing their customers

Please don't ever use MTN as they double billed me because of a mistake they made and have the audacity of blaming me.

I upgraded my 5 contract numbers on the 29th of November and was told that I would be prorated for December as the billing period started on the 27th of November. At the beginning of February I realized that my bill was 190% higher than anticipated.

When I interrogated the statements from my upgrade I realized that they didn't prorate my previous contract rate for only the first 2 days of my billing and charged me a full month. The next months invoice now also included my upgrade charges, my prorated value for December and a full January.

I have received the most idiotic responses and the latest is that it is my fault because I didn't cancel my previous contracts. I went in store to avoid any hassles but they also blame the MTN branch as if they are not part of MTN. They refuse to take accountability of this mistake and just blame a loyal customer of 21 years for not doing something that is clearly their responsibility.

I guess loyalty is overrated and when my contract comes to an end I will be looking to support someone that values their customers.