Airtime theft by provider

MTN has been a horrible service provider the past couple of month, their service sucks and you get excusses all the time you call. I loaded airtime on the 16th Dec 2018 for R160, bought their summer deal for R130, next thing my airtime of close to R18 disappears, without me making a call or anything, they told me i wasnt subscribed to anything on that day, and told me to call within an hour, i did that and was again told to call after an few hours as their system hasnt updated. I called yet again and was told it will be escalated and a call would be logged, 7 days down the line, still no feedback, i called again and the lady i spoke to said she is also logging a call and said we will use same reference number. Till today no one is telling me why my airtime disappeared, bearing in mind this wasnt the first time my airtime just disappears. They disgust me how they dont handle complains at all. They have no sense of customer to them and dont care whether they loose us or not. I cant find the refer number anymore since its over a month just trying to resolve a simple query