Mtn worst ever!

They chow airtime and data like no other service provider. I bought R50 airtime and when I wanted to load data I was told insufficient funds this was literally directly after buying airtime. I then go to check my balance and I had R28 left. Where did the other R22 gone?????? Also, I buy a data bundle within seconds it's depleted. This is ridiculous, worst provider ever. This is ****************!