Spar Milk expiry date 18/3/15 sour not exchanged

During last week we purchased 4l of Spar fresh milk, both bottles dated with an expiring date of 18 March. On Friday evening 13th the one that was already opened had a slightly sour smell, by Sat morning it could not be used. We opened the 2nd 2l and by later that day it also was sour. My husband went to Acres Kwik Spar, 1 block from our house and the manager Vuyo flatly refused to even look at the milk let alone exchange it because we did not have the slip. Since we live behind the Kwik Spar, the chances of us driving to another Spar in another suburb is ridiculous. Surely Spar branded milk well within the expiring date would be sent bay to DC. Incensed I went back on Sunday in the hopes of speaking to a manager with more sense, but alas I was dealt with by a young lady in the same off-hand manner as Vuyo had treated by husband the previous day, claiming it was company policy. We hardly ever even take my slip from the cashier when running in for milk and bread. Not once did they apologise or offer to phone one of their senior managers. I asked them if they were prepared to lose our daily business over R36.00 and they were. Greedy Retailer - no more will you see us.