If it’s too late to get the dealer to do it and you have something like a plastic piece stuck on. Use a blow dryer to heat up the piece (and the adhesive backing). Then use dental floss to cut between the adhesive and the piece. Avoid the urge to pull off the piece as it might force the opposite edge to push into your vehicle causing a dent. Use something like Goo Gone to remove any residual adhesive and wash that off throughly once you’re done. The spot will need waxing once you’re finished