On orders from General Motors" Oldsmobile division, regional Olds dealer agency Roberts & Russell, Knoxville, Tenn., made some changes in its TV spots that are to run nationally during the fourth quarter. According to a supplier close to Olds, the agency used actors giving testimonials for their Olds" vehicles. That's an FTC no-no, unless the ad clearly states the people are actors. The new version is more product-oriented, with voiceovers touting values, says an Olds dealer who saw the ads this morning. The ads break Oct. 3 instead of this week.