Annoyed and Disappointed

Quite frankly this has been the worst upgrade experience I have ever had in my longstanding relationship with your brand. My upgrade request was completed on the 26th November 2017 and I received a notification by email with reference number N4BGF3 and that I will be contacted within 24 hours. 52+ hours later I had to call ********** 4 to have this upgrade finalised. Your own Delivery T&C's states that delivery of the upgrade device will take place the following day providing completed before 12 pm, My call on the 28th was completed after 12 pm so by your own T&C's I should have received my new device by the 30th November 2017, the next working day. On the 1st of December, I contacted Customer care to query my delivery and was told delivery would take place on the 4th December, guess what no delivery of my device. I Followed up today again and was told by the consultant after being on hold for more than 25minutes that there was a backlog due to Black Friday promotions. This is not good enough, surely one plans for and puts in contingency plans for this kind of promotion? I am completely dissatisfied, irritated and disappointed with the service I have received on this occasion and seriously reconsidering my ongoing loyalty to your brand and services. I'd like urgent and definitive feedback as to what will be done to remedy this obvious service failure on your part.