Will not return item

I purchased a medication from clicks lenamet instead of lenapain .I went to them an hour later and they refused to change the meds it was an error which was because of the name of the meds but the dispensary refused to take or back and give me the correct medication there was no signage staying that the item cannot be changed.i would understand if I came through a day later but I drove home and came right back .I have photos as proof that there was no such disclaimer regarding the return of the meds and what makes me more upset is that when I brought it to their attention they went on to look for the sign which was not there.