Vodacom nightmare experience

I recently took a contract for data and modem device at Vodacom 4U in Centurion Mall. I was told by the sales rep if the device is faulty within 7 day it will be replaced. The device started malfunctioning within 3 days after purchase. I returned it to Vodacom within 7 days after purchase. It has now been 2 weeks Vodacom 4U Centurion mall has not said anything. So today I went to Vodacom Centurion Mall to find out the progress with my new device. Vodacom employees told me the most shocking story. I have been told the manager is on leave and my query will be addressed the day he comes back. Seriously? I do not have internet connection at the moment but I am expected to pay my first instalment at the end of the month for a device I do not have and for a service Vodacom never rendered. How can this be fair Vodacom?