MTN where did my airtime go!!🤷🏽♀️

I have been noticing that data and airtime just disappear from my phone before I even use it. Yesterday, I purchased R60 airtime and made one call which was not answered. A few minutes later I made another call only to be told ‘you have insufficient airtime to make a call’ ! This is not the first instance this has happened and I have been stupidly buying more airtime and data only for it to disappear into thin air. This is a rip-off. I don’t know what problems MTN is having but us customers are really suffering! MTN must get its act together!😡