Depleting data and airtime

Hi, I believe there is some ********** activity happening on my phone ********** - at 10:55 I recharged with R50.00 and again at 17:42 yet my airtime keeps disappearing or being depleted without me making a single call - this is not the first time that I am voicing my concern with the network and how I have to recharge a million times a day just for the data/airtime to disappear. I have a primary number that I use, so my vodacom sim card is mainly used to make calls after 20H00 to another vodacom number, so for me to spend so much money in a matter of hours is absurd