Bad service and disappeared data

This is to log a formal complaint as I am unsatisfied with the service I received from one of MTN consultants, which is Miss Nomfundo Gumede. I called the call center to check what happened to my day data of 10 GB, I receive the data at 12:24 and immediately after I saw the sms, I checked my balance to ensure if the data is really there, only to find 5gb of data. I am asking your consultant what happened to another 5gb and she says she does not know and she was willing to let me complain as she also knows nothing about the whereabouts of my data that disappeared. I was at work and not in the internet and you can tell me what could take 5gb of data from 12:24 to 12:30 which is 6 minutes, what happened?