Santam refuses to take responsibility

My family and I recently bought a property in Westville, Durban. The property had had building repair work done to a retaining wall that collapsed during the flooding last year. The repair was done prior to us buying the property and was part of the sale agreement (that the Sellers would repair the wall using their building insurance through Santam). The value of the repair was about R500k we were told. The Sellers were in the process of emigrating and informed us that Santam would manage the repairs. The wall was repaired by a construction company and then signed off by an engineering company, both appointed by Santam. Less than two months after the repairs were completed, and just after we had moved in, the wall began to collapse again, and our boundary fence that rests on that wall fell down. We had an independent engineer assess the situation, and he wrote a professional report that indicates poor workmanship on the part of the engineer and the construction company. The sellers have emigrated, our insurance company (Standard Bank) have rejected the claim, and the Seller’s insurance company (Santam) are refusing to take any responsibility. We have now been left with the problem, which puts our entire asset and our livelihood at risk.