Missing Airtime

My airtime disappeared on my phone and when I contacted MTN customer service I was told that my airtime was finished because I connected to internet while not having data bundles on my phone which is not true then the consultant advised me to speak to people at 3G department to check for me what could be the problem, to my surprise i get different story that their system don't show that my phone used airtime for internet of which the costumer service consultant said to me that on his system it shows that my airtime was used for internet and by then I had data bundles that were used for internet. According to what I heard my airtime disappeared with no knowledge where it went. 3G department I spoke to a lady called Rachel Ntete who explained that my airtime was not used for internet and had no idea what happened to my airtime.