Blue Bell Mint Chocolate Chip ice cream, why is it grainy?

I love mint chocolate chip ice cream, it's one of my all time favorite flavors, and blue bell ice cream is one of my favorite brands. Tonight for the first time I got mint chocolate chip ice cream, and the ice cream is, well the best word I can describe it as is grainy. It's like there is sand in the ice cream, it is terrible. I also got butter pecan so I tried that is it is delicious no grainy texture at all. Is this the way the mint chocolate chip flavor is or did I get a bad batch!? I want to know to see if I can get a refund for it, either way I am gonna write to the company and complain.