MTN IS *****ING OUR DATA AND AIRTIME

I am a prepaid customer. This problem has happened more than once, in fact, in the last two months it has happened four times! I know exactly how much airtime and data I have in my cellphone because I make a note of what is left every time I make a call or send a Whatsapp and use it VERY sparingly as I am a pensioner. My airtime usually lasts for ages. My data too because I use it mostly on Whatsapp. On 20 October I still had R142 airtime and 92MB data left. I wanted to make a call in the morning and a computerised voice said I do not have enough airtime to make a call !! What the?? I checked and found R89 left. What the?? The day before I had R142 and had not used it at all! And to boot, even if there was R89 you mean to tell me, MTN, that one cannot make a local call on that???? Trying to get hold of MTN is like trying to get hold of a needle in a huge haystack. But wait a minute!! That very afternoon around 15:30 I checked my airtime and lo and behold, the R142 was back!! What the???!! This has happened before. I asked the residents on my local neighbourhood community group if anyone has had the same problem. Amazingly 5 residents posted that they have all had the same problem and in fact, exactly like mine. Their airtime disappears then they can't make calls and then the airtime just reappears. MTN RIPS off customers!! They need to be investigated. It is bad enough that their data is so expensive, now they still ***** our airtime!!