A rolling code is a protocol used by garage door openers to keep your door safe and secure. When the radio signals from your remote control are broadcast to your garage door opener, it uses a specific code to communicate. Older models used the same code every time, making garage door openers vulnerable to burglars using a radio frequency identifier device.
Step 1: Check the metal tracks inside the garage. Look at the mounting brackets that hold the tracks to the walls. If they're loose, tighten the bolts or screws at the brackets. Working inside the garage with the garage door closed, examine the tracks for dents, crimps, or flat spots. If there are any damaged spots, pound them out with a rubber mallet, or with a hammer and a block of scrap wood. If the tracks are badly damaged, they should be replaced.
You might genuinely need some extra parts when you thought you simply needed a broken spring replaced, and a good serviceman will perform a simple inspection to identify such parts. Nor is it unreasonable for a business to charge separately for a service call versus repair work actually performed. But the best protection for you as a buyer, being somewhat at the mercy of whomever you decide to bring on site, is to understand what is being done, and ask intelligently for a clear explanation or demonstration of why extra parts are required.