Bad service

A couple of years ago I bought a cellphone(mobicell) at Edgas active sebokeng store which gave me problems days later and I exchanged it with another phone (Vodafone) now and I thought the store will communicate my the insurance as they initiated the deal and the problem is my phone is lost it and as I have cellphone insurance but now I have been sent from pillar to post about this issue. When the phone was exchanged no one informed that I should contact the insurance department so now I do not have a proof of exchange but I have paid all these years for a cellphone insurance but now no one is willing to assist me this issue.