Product support

I purchased a Samsung S4 from Kalahari on the 11th of November 2014. In January, the phone started giving problems. The phone would switch itself off, indicating that the battery is flat and then, once plugged in, would say the battery is fully charged. The phone was taken to Samsung's service center where we were informed that the phone was manufactured in 2013 and that we would have to prove that the phone was purchased within the warranty period in order for them to repair the phone. For this, they require an invoice which has the serial number of the phone indicated on it. Kalahari's invoice only indicates an ISBN/barcode which is not the serial number of the phone and is therefore not acceptable to Samsung as a proof of purchase. I contacted Kalahari on the 5th, 6th, 9th and 12th of Feb to request an invoice with the serial number attached and have been told that they are awaiting feedback from the returns department. I find it unacceptable that Kalahari does not document the serial number of products sold if it is a requirement for warranty from the original manufacturer. It effectively means that any samsung product bought through Kalahari will not be supported by Samsung