Buy online but go to branch to resolve issues

I recently bought a prepaid K203 device on cash from Neotel. On receipt I discovered that the device was labelled void. I then contacted my sales consultant who said I can use it its just a label. I discovered that the device could not charge and contacted the sales consultant again who told me to go to a branch. I could go to a branch for something I bought online and hence asked their customer service to pick or up the phone or exchange. On the 30th of October which is 2 months from the date of purchase freight care logistics came to deliver the phone and I had to test the second device to se if it work. When we tested the product it came on but was showing a blank white screen for about 10 minutes. The logistics personnel witnessed the fault of the second device. I decided to send both devices back to Neotel . I then phoned Neotel to request for the refund and they declined because I was not on contract but on prepaid. Neotel can keep both the money and the handset. They cant keep tossing me around. Clearly once the money is in their bank account they don't bother whether their products works or not.