I have upgraded, but am without a phone

I upgraded my MTN contract, and very quickly recieved the new phone. The phone was faulty! MTN told me to take the phone to a MTN direct store, which I did the very next day. I took the phone to the MTN store at the Key West Mall, and they took the phone and handed me a collection number and told me that MTN would be sending me a new phone. I have been trying for 2 weeks to find out why I haven't received my new phone. When I phone MTN, they transfer me to Velocity, who have no record of receiving the phone, and then refer me to the store at Key West, who are adamant that the phone was collected. When I phone MTN again, I get transferred again, to Velocity, who need the serial number of the phone and tell me they don't know where the Key West Store is. I then tell them that I got the address off the website for them, with a phone number, and give them all the details. Every time I phone, I am assured I will get called back with the details. After 2 weeks, I have yet to receive a phone call. I am so sick of being passed around from MTN to Velocity to the Key West Store!!!!! Apparently I should know the serial number because MTN doesn't!!! Just lazy to check.