Fed up of poor service delivery

Hi, so in end of july my husband upgraded a contract we have with mtn from a cellphone to a laptop package. First it took about a week to successfully complete the upgrade because their systems are forever offline. The package included 4gigs day and 4gigs night data(8gigs data) in total per month. The data is credited on the 12th of every month. On the 12th of august the account was only credited with 4gigs data(2gigs day and 2gigs night) , the same data was credited on the 12th september.My husband made 5trips to the store(mtn promenade mitchells plain) of which he was only seen to thrice & several calls to their champions. One champion had the nerve to ask why we called so long after the data was credited. My husband told him because going instore has proven to be unsuccessful ,so he's trying an alternative measure. He contacted one of their consultants Charlyn Tayer ,who gave him directive about what to do ,but has had no success, he brought it to the attention of the consultant who initially helped him Mercia Pegram,who acknowledged the data we're receiving is incorrect. So he's been debited twice for incomplete service. Everytime he makes contant with Mercia she either doesn't respond at all or she promises to get back to him,but never does.Today 2 October he contacted her(mercia) she said she would call him after 9am, its 9:30 & no call as yet, exactly what we expected. Their service is pathetic and the consultant ***********,with follow ups. Its frustrating having promises made and then its not being followed through and paying for something we're not receiving the full service of. This is getting tiring,going from pillar to post without success