lightroom processing, then printing problem...

I use lightroom to edit my pics..then I save them to a file and print them on a CD using 300dpi...

today...I went to Wal Mart (don't flame me for wal mart) they were prints that were not important, just for reference for me...

when I picked them up...it was like the heads were cut off..some seemed enlarged but, were cut off..

Did they seriously NOT look at the file and just print them...

Or, did I do something wrong, besides using Wal mart.

There could be several things happening, but my guess is the following. You are printing a image with the incorrect aspect ratio, ie your image has a 3:2 ratio and you are trying to print a 5x7.