Data Bunndles issue

This is the 2nd time this happened to me, I received an SMS on Saturday that im only left with 99MB but I ddnt worry about it because I thought maybe this was right because its has been a while since I loaded 2GIGS of data on my phone. a few moments later I get another one saying that my data is finished & what surprised me is I wasn't even using the phone or browsing nor surfing the Net, I decided to load Data later during the day which was a once off data which expires after 24 hrs of loading it, chilled as usual not even using the phone but 30 min to an hour of loading the data I get an sms saying that im left with 99mb of data without even being active on my phone, and I started to suspect that there must be something wrong, and yesterday same thing happened after I tried it 3 times of loading R10.00 once off data. Called the call centre I was not helped I spoke to Thulane who literally hung up on me, called again & asked to speak to the Manager & Mandy said Menzi Magubane would call me back but I never received a call at all. this is unacceptable