MTN for real?

My wife took out a contract with MTN in January 2020. This promotion was as advertised 10gig data day and 10 night plus additional 30 day and 30 night. We went to the Somerset branch on 3 different times and with no positive outcome. The problem is that the 40gig day time data last only for 2 weeks. We don't stream or download anything but on the first day of each month they will take their monies although according to them (mtn) we have used up all our data. We get our top up on the 12th of every month. How is possible to use 40 gig of data in 2 weeks? My wife and I are at work during the day. 3 months ago we talked to one of the consultants at Somerset branch and he did logged our complaint and he promised if we were to experience this problem again he would ask his manager to help us to cancel the contract. I would like to challenge MTN to call my wife and explain to her why we can't have our full data of 40gig because we buy additional data for our phones. Yours truly anti mtn. Mark Peters (Linda Peters - acc no. A*** / cell. ***)