You would want a civil litigator who brings Plaintiffs' claims for breach of contract. However, if your claims are very small, it might not be cost effective to actually hire an attorney. You may want to consult with an attorney to find out about costs and how to proceed if you bring these claims by yourself.
A general practitioner is probably sufficient. Depending on the type of service business you have you may have a garageman's lien or similar lien for your work. Perfecting that lien requires certain action on your part. Consult with an attorney to determine your options.