Mtn ****ming me of my airtime

I am very angry and even thinking of leaving this service provider 😡 I bought the R349 100gb special unfortunately I was owing so they took their money and was left with R279 that was okay I then bought an additional R77 airtime because I need data for work, tell me why my balance is R311😡😡😡😡 okay I then said let me just take airtime advance was going to call them in the morning to enquire about my airtime. I then received message telling me airtime advance has been loaded when I checked the balance IT HAD GONE DOWN FROM R311 to R305😭😭😭 how is that even possible 😭😡 I want my money back and for my data to be loaded. I DO NOT HAVE ANY SUBSCRIPTIONS. Is this how mtn repays their tunure customers 😭😭😭😭😭