C***** Authentikos Greek Yoghurt

I am mortified. I love C***** Authentikos Greek yoghurt. It's the only yoghurt we eat and have bought it weekly for years. Two weeks ago I bought one at Checkers Selcourt Towers, it was runny and sour, though it wasn't expired. I took it back to Checkers and they said we can have a new one, that one too was runny and sour. My mom in law took it back a 3rd time, the lady that worked for Checkers went to get one, she opened it and said it was fine, she clearly does not know what Greek yoghurt is supposed to look, smell and taste like, When I got it and opened it and tried to stir it to make it thick....guess what....It was also runny and sour. This yoghurt used to be the best yoghurt. Have you changed it C*****? It's not at all nice, it's like having sour milk. Unacceptable.