MTN is Ridiculous

I have emailed MTN last month to inform them i get 40 gigs of data a month as per my contract. My mobile data was off and my new data kicked in. I was only given 36 gigs this month and last month. I emailed this to them last month and they said i have used accordingly. How can i used 4 gig every month that i never had? My data was off wifi was off. Apps all closed everything cleared and i was still credited today with 36 gigs. Yet mtn sends an sms i was credited with 40 gigs. My data was off so my phone couldnt be using data. Mtn is ridiculous i cant wait to change over to another network provider the moment my contract is up. They not even bothered into looking into it. They just gave me impossible reasons this could have happened.... BUT my mobile data was off even on waking up and checking my balance before turning it on. Not once did i have an issue when i had the 50gig data contract but i really need to leave the mtn network . Just not worth it anymore