Disappearing data and airtime

I have just recently signed up to cell C and so far its been not good

The phone used R150 of my airtime as data , which has never happened before . then i loaded on 200MB of data and it was gone in 20 minutes. I was not doing anything major on my phone.

iCloud back up is turned off , roaming is turned off. wifi assist is off .

i called the call center and the first agent , pretended there was line disturbance and cut the call ..

The 2nd time i called I was told I have to wait till the end of the month for a data report ... Which means that what ever the issue is it will only be resolved in 2 weeks time , can you imagine how much data I will have to load on to make it till the end of the month

This is leaving a very bad taste as I have just joined cell C , depsite their bad reputation is still did it ...

So I want an explanation for what the hell is going on here, because I have never had this issue before