MTN ***** deals

I took out a LTE contract with MTN in July last year, All has been going well until now. On 16 Jan I was not able to connect as apparently we had used up our data - 220gb since 17 December. My usage report on 24 January showed 23.58gb had been used since 17 December and my balance on that day was 86.67gb. If I add these two amounts I do not get 220gb. I have been tweeting MTN and emailing customer care. They refuse to call me and when they reply they just say my data was provisioned.