Broken bags

I bought some groceries at Pick 'n Pay, the lady at the till asked me if I would like to purchase bags as well, which I said yes to - as many bags as needed. When I left the store everything seemed fine. <br> When I got home the bag broke as I took it out of the car, first the handles and then underneath, and my goods fell out - I bought pasta sauce to make the evening and it shattered to the ground (the pasta sauce was not usable at all). I went to the Pick 'n Pay where I purchased it from and they don't want to give a refund. This isn't my fault at all and should be reimbursed for it - the lady at the till should check the weight and if the bags are fine. In fact her attitude wasn't pleasant.