Using all airtime for data and not data bundle

<p>Today MTN used all my airtime I purchased yesterday when I still have available data on the 1gig bundle I also purchased yesterday. this is getting rediculous, MTN does this on a regular basis and I have lost thousands of Rands over the past 2 years. MTN is very cleaver as they use all your airtime for data and then suddenly when all the airtime is finished they send an sms notifying that you are using out of bundle data but like I say very cleaver on there part wait untill the airtime is finished before notification is finished therefore very nicely lining the coffers. </p>