Airtime keeps on disappearing

My mom has been complaining about airtime disappearing from her phone but when we phoned Vodacom they still can't assist her until it happened to me. Called them and even escalated the matter and I was told of the number I have dialed at the certain time only time only to find that time I was busy with an incoming call so where did my airtime go Vodacom. Good thing I even canceled their contract because I don't want anything to do with them anymore. The last agent I spoke with was rude rude, so disappointed after having been with Vodacom for more than. 10 years