My airtime has been running down automatically

My airtime balance has been running down the whole week, automatically from a couple of hundred Rans I have nothing and I barely phone now my phone won't do anything, I even added R60 on Saturday, it's gone? Now I have 200 mb but I cannot use anything, even when I had airtime and I tried to phone it says your airtime is depleted please recharge. What is happening here I want a detailed report of how my airtime got finished I will even pay for the report, I am tired of MTN when I received my statement in the month, I was able to view other customers statements online, ur systems are messed, last month when I checked airtime, I had R2 then a few hours later my R400 was back what is that I try calling and all I get is voice prompts, this is **** I want an answer!