Bad aftersales service from Elasto-Flex in Durban

This company came and repaired some roofs in our complex last year March and it appeared that they had done a good job but since then the roof on one unit is not right. This company is supposed to have a guarantee according to the paperwork we have but I have tried phoning the owner and I have sent numerous emails but to no avail. I did speak to the owner once about 3 months ago and he promised me they would come out the following week but never arrived and I haven't been able to contact him since. It seems like they make these wonderful promises but as soon as they are paid that's it you are on your own. We are not sure how to go forward with this as it is now going to cost us more money to get another contractor in to do the repairs and we are a small complex with limited funds, very frustrating and sad.