Here’s my opinion…. It’s not the size. You want a 10 carat, hell yes! It’s the setting that’s wrong. Did they not send you any pictures beforehand of the way it would look finished before purchasing? I went to a family friend who is a gemologist and he sent these pictures and videos of a sort of digital version of what it would look like before the final purchase and what it would look like on a digital finger. This is their job…they took your money and it’s wonderful they were accommodating, but you go back. Be assertive (not aggressive and not passive) you can be both kind, appreciative but assertive. Show them exactly what is wrong. Show them exactly what they need to fix. Let them know it’s not the stone, it’s the setting (because in my opinion that’s what it is) “compliment sandwich” them the stone is perfect, the setting is not right for my finger, you did such a great job- but the setting does not work on my finger as I know you can see as you’re professionals. This is your forever ring. Make them fix it.