If it doesn't "fit" in your garden and you can't return it, then find someone who does have the room and give it to them. This is really not something you want in a container long term. On a very temporary basis, sure, but growing a tree like this in a container indefinitely or on a permanent basis is fraught with complications. But the biggest drawback is that the tree will not be allowed to develop its very characteristic flat, wide spreading, almost tabletop habit. Combined with the white flowers, that is its most notable feature.