Rotten custard with in a day.

Its so disappointing to buy something you love and get disappointed when you find it rotten. Im not sure if it the packaging or it the product it self. The ultramel custard gets rotten with in a day of opening it, when you eat it the next day if completely off and tastes terrible. this has happened more that three times of buying the product, i keep going back to it because its what i grew up on, but lately it has gotten so bad. ive bought other brands and did not experience the same thing. So after doing the comparison, there is definitely something wrong with ultramel custard. Danone must look in to it because they are loosing loyal clients who loved their custard. Like literally when you taste it the next day or two it taste very bitter and its very watery, very awful. Its very disappointing, because you have to throw the whole thing away, such a waste of money. I tried to take it back to the shop, but they refused to change it because it was still within the expiry day, which was not fair because it got rotten in the fridge tightly sealed. I discussed with my colleagues and they shared the same sentiments, hence they advised me to try other brands. Im sure its not the first time you hear of this. Please do better with you packaging or the product it self....