Airtime dissappearing

Ive been a loyal customer of vodacom for years now on prepaid.

Recently ive noticed my data has been running out much faster than usual even when all my background apps are closed.

They have become unaffordable, yesterday i bought R30 airtime and 100mb data bundle, this morning i check my balances to my surprise my data was in tact but my airtime balance was at R2 airtime advance took their share and i was left with R19 airtime when i went to sleep last night, but bare in mind i bought my airtime and data seperately...can someone please explain to me where my airtime went?? I used it for work purposes why should i stay with vodacom when i get dropped calls, slow network, expensive data charges and prices and my airtime thats dissappears, i tried phoning customer care this morning however couldnt get through due to high volume of calls they are receiving i should try to call again later, i though vodacom was one of the best network in S.A!?? Whats going on?? Can this be sorted why is everything so expensive but the service received isnt worth more than a 5c!????