Data Issue

I have been a loyal Mtn customer for sometime now and for the past 2 days I feel cheated on and betrayed, yesterday I loaded data on numerous times and every 5 minutes mtn will send me an sms that says my Data has been depleted. The callcenter has been no help either because when I call in I am told the sytem hasn't updated yet??? Working for a network myself I know about the data usage structure and how it works so I know vey well I won't exceed data within 5 minutes of using the Internet. This has frustrated me so much that I am now scared to load any data on my account, today was the worst!!! I loaded 50 mb because I was scared to load more it was exactly 6:30 in the morning at 6:35 mtn sent me an sms that said my data has been depleted and it is so funny because my only active application was whatsapp all my other applications were off. It is definetly not my phone as a person who knows my phone very well all my automatic updates were off I need an explaination as I am not willing to port out or use a different network this is definetly bad service from Mtn. I am now left with a phone without Internet as I am scared that I will load more and it will be depleted 5 minutes after