data and airtime theft

Loaded R 110 airtime today and bought a 250 meg data bundle at 1837 this evening, confirmed by SMS. By 2100 all data and airtime has disappeared even though the phone was not in use. No warnings, just a zero balance. Impossible to get through to their call centre. App data usage shows less than 30 megs used. Vodacom please explain your blatant ****. This is not the first time, previously my balance went from 150 megs data and R 50 odd rand airtime, this is when I boarded an aircraft. When I turned the phone back on every thing was gone, how the hell is this possible? My other Vodacom number is data only and used for wifi and this NEVER happens. It is also impossible to get through on their 111 number. Please explain and refund and don't give me your **** about data usage, I know EXACTLY how my data is used