The service called "copyediting" corrects errors in spelling, punctuation, grammar and style. As a group they are called "mechanical" errors.
Copyediting may be requested together with, or apart from, manuscript feedback. Proofreading and fact-checking also count as copyediting. Always have a second person check your manuscript and your page proofs for errors. The author alone cannot catch them all. I have seen books whose whole first printings had to be destroyed because they contained an embarrassing number of errors —a very expensive outcome for an entirely preventable problem.
The fee for copyediting is .03 per word of your manuscript. Remember, it includes fact checking.