No matter what business you are in you'll always have people trying to compete and undercut you. You've just got to make sure you are providing the best service you can at a reasonable price, and that doesn't mean offering stellar services and underpricing it.

Even if you lose business temporary if you provide a good enough service the word will get out and you'll continue getting business. Whether this is spam or not probably depends on the person who receives the message. If they consider it spam they may report it and it may get dealt with if an admin agrees.