It is a very good idea to have a follow up system. Most people will be amazed that you do it, many of them will use the opportunity to praise you or your staff. The few that do tell you things you'd rather not hear are doing you a favor.
Most people do not complain about bad service. Think how many times you have had bad service or poorly prepared food at a restaurant and were asked "Was everything ok?".
Most times you say "sure", and just pay the bill.... but you never go back.
I read of one study that said 26 out of 27 people will not complain about bad service, but will not use the company again.
I think its well worth dealing with a few people who might take advantage of you for the overall benefit that such a good customer service practice can mean to you.
I've been working with carpet cleaning companies as a trainer, consultant, or often just a "sounding board" since the late 70's. The one thing the veterans out there who make a practice of following up on every job told me since those days was this:
"If there is any one thing I do that is my "competitive advantage" over other cleaners, especially the good cleaners, is the fact that I or my (wife/representative) calls after every job to make sure everything came out just like we promised"
I think its advice worth taking.