as the software lab use does not support raw format
if the lab really really really want to print your raw files, there have to open it at photoshop and convert it jpg, than use the lab printing software to do color and density adjustment from there.
do note each individuals camera made and model have different RAW formats, so the labs may not able to open your raw files in their photoshop. and most of them are not very good in photoshop, unlikely willing to take your orders.
you have to convert your RAW file to jpg or tiff yourself, please note not all labs accept tiff files, as tiff file are very much larger than jpg, they worry it may slow down or cause their system hanging.
Actually, the idea behind shooting RAW is to allow the photographer maximum flexiblility in the manner in which he may edit the image. If you prefer to send the images straight to print, you're better off using the JPEG format.