First off I donīt think your prints look bad at all, great graytones but sure an overall low contrast. But when you send it of to a lab it is hard to say where in the process it has gone "wrong". If you rate your film at half the iso speed and just send the film off the guys at the lab probably process it at itīs normal speed. Further on when they actually do the prints its up to the machine to interpret your negs and do something with them, that is mostly a lottery game unless the lab is truly professional and do every print by hand and you can tell them how you want your prints. I donīt think that is the case as it is very rare (and expensive).
As a comparison, I have the past years sent a few rolls of Kodaks BW400CN to labs and have always been extremely disappointed in the results. This has always been because the lab has done a crappy job and their machines could not handle the negs in a proper way.
Obviously the best thing to would be to develop and print yourself but I imagine that you donīt want/can do it so Iīll leave that. The first thing I would try is to shoot the film at itīs standard speed. But unless you can talk to the labīs staff and ask them to make the prints with more contrast or to develop the film longer (more contrast in the negs) its probably not much that can be done from your part. I donīt think you are doing anything wrong when you shoot, the problem lies in development and printing I suspect.