Customer taken for granted

I bought 3 phones in October at PEP southdale and 1 of the phones had a problem. I took the phone and box back only to be told that they cannot assist me because the phone IME number is not on the box and phone. I took accountability on the IME number missing on the phone because my son took it off. With the box IME number, it is not true that it was taken of because I removed the phone and charger myself and handed and gave it to my son and I took the box and kept it, as I know that it is needed when the phone has issues. I must say, the branch staff did assist me well, we reached this stumbling block which is out of their control. I then reported to their head office the issue and till this day I have been told they're waiting for the area manager to respond and she/he has not done so. It is not fair for me after purchasing 3 cellphones and mind you "they all came from display" and I'm not returning all but one and I'm not even considered as a valuable client or taken serious. The area manager took my matter and felt it was not worth responding to in my option and it is not fair treatment from such a big store. The reference number for my query is ***

NB: I was told that they can not even taking it in for repairs due to this IME number. Also note that I took the phone back within the 7days period