Mc Donalds sour milkshake

I have ordered 2 milkshakes from Mc Donalds, upon taking the first sip it was the most awful sour taste I have ever experienced. I took both back and they couldn't even apologize, all they wanted to do was give me ice cream in return. After a big fight I got my R72 back but not once have anybody apologized. Its been 3 days now and my stomach is still upset from the sour milkshake.