Targus 17.3 laptop bag Lifetime Warranty - Poor after sales support

Purchased a Targus 17.3 laptop bag from PCShopper. This carries a lifetime limited warranty. On the stitching of bag has come loose. PCShopper have contacted supplier Tarsus Distribution from Woodmead. I have not had feedback regarding the way forward. I have been to Tarsus Distribution( Woodmead) and Axiz Pty Ltd. (Midrand). They require the original receipt/invoice showing purchase from them. I only have the invoice from PCSHopper. Poor after sales service.