Sony M5 advertised but never had stock

I called Mtn Direct regarding the Sony M5 that they have advertised so that I can apply for an upgrade that is due to me. Agent says that there is no stock available and that I should try during the last week of the month however if there is no stock the deal will be over.She advised that it is possible that a store in a different region will have stock and I should check there. She could not tell me which stores will have stock and that I must call some other number to check. I also called stores namely Musgrave and Randburg(Pavillion, Chatsworth and Gateway do not answer) and both confirm that they have never had stock of this device and it is now the middle of the month. How can a company advertise for something that they do not have or never had. At the end of this month my free upgrade will expire so I am being forced to take a phone that I do not want or cancel my MTN subscription. I am not sure what to do.