Bad service is an understatement

I have never in my life experienced such bad service. MTN's customer service is so bad it makes government organisations look good. I bought a contract phone for my sister and she was due for an upgrade last year in June. Did I regret upgrading with MTN? First they charged me for BIS when I upgraded to a Samsung. Once notified, I was told they will credit it back to me, which they did. A month later, they started debiting different amounts, from R372 to R420 till to this day, meanwhile I signed a 369 top up contract. I notified them and still nothing was done about it. Decided to go into a branch 2nd Apr since clearly they have the worst call center ever, only to be told I'm being charged for extra data and airtime. Why on earth would they do that when I always top up when the data or airtime is finished, and to make matters worse, I hardly ever receive or use \the extra data". When I enquired about it"