Posted on behalf of my colleague Lora Pabst:

Hundreds of you have asked Whistleblower for help. While we can't investigate each tip, we want to share more of what you tell us. In 2009, we started publishing a few tips each week to stimulate online discussion and create ways for our readers to help each other. Unlike our news stories, we have not verified this information, so we do not include the names of the parties involved. If you have a tip, send it to whistleblower@startribune.com.

A Minneapolis man went to a national tire retailer to use a coupon for an oil change and tire rotation. He marked the rims of his rear tires so he could make sure they were moved to the front.

When he picked up his car, he was told that the tire rotation had been completed. But thanks to his foresight, he was able to tell that the rear tires were still in the same place.

He confronted the salesperson and was given several excuses for why the rotation didn't need to be done. When he pointed out to the manager that his invoice said the tires had been rotated, the manager apologized and finished the job while the customer watched.

He wants to know: How often are consumers charged for services they didn't receive?