Gift exchange

My mother received a gift recently from my sister who doesn't live nearby a week ago we went to try and exchange it the item is in good condition unused and with a tag we had asked them at the beginning of the month about their returns policy on gifts and they had even scanned the item to check where it's from on that particular day my mom couldn't find a suitable item hence we didn't do an exchange we go back to the store yesterday and they refused out right to do an exchange on top of that they refused to even look at the item instead unosipho that helped us at their gateway branch was rude and short please resolve this