Poor service yet again

I app**** for an upgrade on 28th November 2021. I did call the call centre and was advised delivery would take up to 10 working day and the courier company would contact me. On Friday 10th December 2021. I called again and mentioned to the consultant no one has contacted me. She stated no stock available. 10 working days have gone by. I have been the one calling Mtn. There has been no updates from Mtn. Must i go to a company who can deliver in time. This is really poor service.