Over selling and zero delivery

I was contacted by Bongani Mchunu on the 8th of March to inform me that my cellphone was due for an upgrade. We agreed on the device that I would be upgrading to and advised that the device would be delivered to my work address. The agent advised that due to my work address I should expect the delivery in the next two days (even though delivery normally takes a maximum of 8 days) . I sent him an email on the 15th just to find out what's the hold up and he informed me that the phone would be delivered the next day. The phone was not delivered the next day so I informed him via email on the 18th and he advised that the phone would definitely be delivered the next day as the was a delay with the courier. The device was still not delivered and I informed him of this again on the 25th and to this day I have not received any feedback nor have I received the device. If the device is indeed with the couriers as your consultant says why has it not been delivered till date?