Milkshakes

On numerous occasions we have ordered milkshakes from macdonalds. They are pure syrup. After complaining many times, nothing is done about it. The Isando manager had the decency to tell us the machine had not been calibrated correctly and gave us a different flavor. However it happens at Edenvale continuosly. Why is it that this is happening at all the branches. Is no one cable of calibrating the machines ! Why is head office not looking into this? Needless to say we are done with macdonalds and will no longer be going there and wasting our money.