MTN is a *****

I am on MyMTN Home package of 120G for R269 per month since August. I have noticed that my data is finish early and decided to check it when they upload on the 17th. I did check this month only to find out they are loading 100G instead of 120g, I have been calling them since Sunday but still no help even today. This is ***** because the money they deduct is for the 120G not 100G. Please help