What should I do with a recently purchased item that has a falsified date of expiration?

I recently bought a colon cleansing program from a retail store along with a fews other items, since I was in a hurry I didn’t pay to much attention since the box was securely sealed. That night, as I was getting ready to start the program I noted that the expiration dates were missing, as a matter of fact they were “scratched off” on all the items inside the box, three in total. Only the expiration dates were removed while all the others were left intact. since the box and other packages are made off that glossy white carton you can discern the shape of the number at a certain angle with good lighting clearly showing that those items have been expired for nine months. My first thought was to just return it, get my money back, and try hard not give them a piece of my mind, then I noted someting enven more peculiar, the store had entered a diffrent expiration date on the receit, next to the item. I’ve never seen a store go to such length to sell an item before…what should I do in this case?