What do you do?

[ginger]

If your price board says $3.00 and you try to charge me $3.10, I'll argue over the difference. It's more for the love of arguing than the love of 10c.

[(jeff)]

Take that shit back and throw it at the first employee you see.

[Prodigal Son]

It's still in your fridge isn't it?

[Bristow]

As someone who consumes his body weight in Greek/Bulagarian yoghurt per day, I feel your pain of finding your spoiled treasure. I will say, this surely has absolutely nothing to do with the shop you bought it from, unless the shop in questions produces this yoghurt themselves. If it was a small local store, I would possible call them to let them know, incase it was a bad batch, before a whole bunch of people waste their $5 and then wrongly point their anger at the store in question.
If your local store is a Walmart type piece, then I wouldn't give a shit.

Ultimately, you just have to put this down as an unfortunate event, as I'm sure this rarely happens. (never once happened to me) If it happens again from the same shop/same brand of yoghurt, yeah I might start putting ringing some people up asking what is going on.

[Bunky]

Chalk it up as bad luck, toss it, go back about my day.

Let's just say by chance I'm a really big fan of yogurt, and I really love this brand and it's an important part of my life for some reason...  Then I may write an email to said company producing the yogurt and say something the affect of "hey, I'm not trying to get anything free here, but I bought some yogurt from X store on X day, and even though the seal wasn't broken, when I opened it on X day it was spoiled.  The listed expiration is X.  I eat your product every day, and just wanted to let you know as it pertains to quality control and if I were in your shoes I'd want to know too, because I know some people would make a big stink about it on social media and such, and I'm sure you want to prevent that kind of thing."  yadda yadda yadda blaw blaw blaw, just to make them aware that they might have some faulty lids or something.

If said company gets a lot of these kind of complaints they may look into it.

[Tall Opinion]

I would toss it in the trash. You know, the place where all yogurt belongs.

[Alex.]

Gotta get your dairy some how. How can someone even hate yogurt!?

[Prodigal Son]

I'm down w palek paneer. Fuck m&m yogurt and anything that doesn't have acidolphilus.

[ginger]

Gotta get your dairy some how. How can someone even hate yogurt!?

It's called pizza, give it a go some time.