Argghh - Printing! Do I put a border on my shots?

I am going slowly insane trying to get some images printed for a 6 x 4, 7 x 5 and 5 x 5 aperture on a mat in a frame. When I go to order the image it is making them 6 x 4 but if this is the same as the aperture, I won't have anything to fix the image to the mat. What does everyone else do? So far I have come up with using GIMP to put a .5 inch white border on my 6 x 4 and then think of ordering 7 x 5 to give me the image plus the border. It seems a lot of work to get something that should be (?) simple. All thoughts comments welcome. The second image has a border on it...