You get charged for Services Cancelled

I took up a data contract through one of the sales calls in January. ***) It included a wifi router. when the router/sim didnt work, i called to cancel the deal ***. They collected the devise and sim a few days later and i received notification that the parcel was received. I have been Charged the pro-rata fee (R25) and one months full instalment without having had the opportunity to use it... When I tried calling the number (***)to resolve the issue, I would stay on the line for 45mins and no answer. How does one get charged for services that were returned???? If only Vodacom could just answer their calls. Ridiculous