Mtn
Why did my billing go up

I really don't understand why my bill went up.
I called your call centre and everyone is useless there, no one can give a person a straight answer.
Our agreement was R268.99 for 24 months and for the past 2 months you guys are taking R297.99.
WHY?
I refuse to pay the extra money because you guys are already expensive and charge a lot of data and airtime.
Can I please have my refund and my instalment corrected unless I'm taking this up with CPA.
This is daylight.