Poor customer service

I took two wifi modems by consultant, Tristan, several weeks back. After it only being activated a few days after I got it, the signal was extremely poor. I could do almost nothing on my cellphone. I sent Tristan two emails asking him what's wrong with the signal and got no response. When I got my invoices it was way more than the R89 he confirmed it will be. R300 was debited from my account the 28/02/2015 even though I only had one of the devices. One modem then stopped working. I took it into store on the 26/02/2015 and another consultant, Devon, took the device and said he will call me back the next day. I also informed him that evening that I depend on my wifi and I had no data on my phone. He did nothing about it. I took the box into store before work the next day and Tristan still said nothing or apologised for any trouble that was caused to me. Up and until now no one has called me or emailed me. I'm paying for wifi I'm not using. I'm very disappointed. I gave them a good rating when I got a call for a survey. I'm starting to regret it.