Brocken Phone

When I purchase goods from Cash Crudaders I know I'll save on my pocket and have a close to new ..in a working conditions item....nice bargain..Not something that's not in a working condition... because when they take any product in the operating shop with a valid license all products should be tested...I bought a blackberry 9720 for R1400 when I tested the phone in the shop it was fine ...when I got home it start rebooting the whole day and night...when I took it back the said it was a software problem..fine enough .....I asked them to help me book in the phone or help me to upgrade the software they were to buzzy. That is poor customer service really I'm dissatisfied true...please help