Before you complain to The Fixer, try to resolve your problem on your own. Store clerks and customer service agents are actual human beings - and if you play your cards right, you'll often find success.
-- One definite no-no is to start screaming right off the bat. No one responds well to that.
-- Plant a smile on your face, take a deep breath, and calmly, intelligently state the problem. It helps to have some notes in front of you to help clarify the names, dates and specifics. Be confident, and assume this person wants to help get it fixed as badly as you do. Get them on your side.
-- Tell them specifically what you want, and be reasonable in your request. This gives them a pathway to resolution. -- Make sure you keep a log detailing whom you spoke to and when, and what they said. -- If they can't resolve it, go up the chain of command. Find the manager, then the district manager, then the district manager's manager, and so on. Repeat as necessary.
-- If that doesn't work, write a concise letter that lets the key business people know what the problem is and how you've tried to resolve it. (You can find a sample complaint letter at www.consumeraction.gov.) In your letter, set a deadline -- two or three weeks; whatever you think seems reasonable -- to get things fixed, and say if they can't do it by then, you'll seek third-party assistance. Then, do it.