Airtime not being loaded for 2 months

Hi Vodacom. I have issues with one of my numbers ***. It is supposed to receive 160 airtime on the 1st but past 2 months before the end of the day the full amount is gone. There is no content the number is subscribed to and the funny or weird part is I have WiFi at home therefore to be told the airtime went to apps data usage back ground what what doesn't add up for me as it has never happened. I was not fully satisfied with the call center's explanation.