Bad Invoice (Product Serial Number Mismatch)

The serial number of the Dell monitor I purchased(Invoice) does not match the one on the product.

Also the SSD drive they gave me was used(second hand) and faulty, I was provided with a new one after returning it the following day.

Now I am having problem with the monitor, Dell is willing to refund me as long I provide proof of purchase, so I called Southgate Matrix where I purchased the monitor. They requested serial number of the monitor, it didnt match any records, they requested pictures of the box with all the numbers, still no records of the monitor. After digging through my bank statements I was able to pin point the exact date of transaction, amount, also remembered all the invoice items.

Only then, they manage to pick up the invoice, the problem now is the Dell monitor serial number mismatch. I spoke to Justin and Isaack, the branch manager. Both of them seems reluctant to help, I am not the one who processed the invoice to know which bar-code to scan, one of the reason I shop with reputable retailers, I expect professionalism nothing else.

As mentioned, I already logged a service request with Dell since the warranty is still active. Any form of help and assistance will be highly appreciated