MTN is disgusting!!

I've been a loyal MTN customer for as long as I can remember, even when I changed my number 5 years ago, I still remained with the service provider but recently my data has been disappearing and every time I call and ask them where did all go, they don't seem to care. I buy 2gig worth of data that is supposingly has to last me 7days but it barely makes it to 2days. During the day I use Wi-Fi at work so I hardly even use the data however it still mysteriously disappears, when I call in the call centre the agents have the audacity to ask me, "what do you want me to do?" How about returning the data that you stole from me?! MTN, you ***** from your customers! I am utterly disgusted, in the last 5hours, I've bought data worth R55 twice! Half the time I wasn't even on my phone, care to explain where the data went?