Poor service provider

I am not happy with the service vodacom has been giving me I pay my contact every month, last month I had to call in because R150 airtime magically disappeared I called in and was advised that there are subscriptions taking airtime every day and I never app**** for subscriptions the lady told me she will cancel the subscription and refund me my airtime back... This month again same problem I called in again and was told by the agent and her team leader phindile zibi that there was subscriptions again taking airtime but they can refund me because they only did it last month for a courtesy cause I complained for the first time and that they wil do a investigation... I don't understand where does these subscriptions come from I'm very unhappy because I pay for this service and the simcard is my wifi router which I don't even use everyday.... Very poor service I can't wait for my contact to end I'll never use vodacom again thank u for your poor assistance