The caller's name was Jack Webster, and he lived in Columbia. But he might as well have been Mary Montgomery of Southeast, Hazel Loftwich of Northwest, or half a dozen others.

Jack's problem: He had read a classified ad in Sunday's Post that offered "part-time interior design services.' But when Jack called, the service offered turned out to be architecture, not decorating.

"Doesn't anybody check the ads before they're published?" asked Jack. And Mary. And Hazel.

And me. After hearing from so many readers who felt ripped off by Post ads that didn't quite deliver what they expected, I had a sit-down with Bob Martion, the Post's "advertising ombudsman." Here's what he had to say:

"We do have a problem in that people perceive us as having the same kinds of controls on advertising that you have on the editorial side," Bob said. "But there's really very little you can do to keep a fraudulent or misleading ad out of the paper the first time.

"We of course try to keep out the things that are patently fraudulent. And where we have complaints and a company won't do anything about it, we take their ads out of the paper." Perhaps a "couple of hundred" advertisers have been barred from the paper in the last year under this policy, Bob said.

"But what it comes down to is the buyer, and the decision he makes. You can only go so far in protecting people. Ultimately, the buyer has to decide whether to purchase something or not. We believe we have a responsibility to the community. But we're limited in our ability to check everything, especially classified."

The story they like to tell in Bob's office is about the guy who called to complain that a Post had led him down the primrose path. After reading a classified ad about a $12,500 Mercedes Benz, the caller met the car's owner at Georgia Avenue and the Beltway, paid for the car in cash -- and then wanted to blame The Post because he forgot to ask the seller for the registration and the car proved to be stolen.

Mail order ads are a particular hotbed of trouble, Bob Martin says, and all of them are checked before insertion, especially ads that deal with too-good-to-be-true claims. "We're always on the lookout for $1.98 creeping strawberry plants that are supposed to grow anywhere," Bob said.

As for home improvement, another trouble area, "our people are trained to stop any ad from a company that's given us trouble before. All it takes is a second call on any advertiser saying he isn't living up to his claims, and we'll investigate."

Have you followed up on an ad and found that it doesn't quite pan out? The man to call, whether you're out some money or merely suspicious, is Douglas Dykstra, the advertising department's reader relations representative. The phone number is 334-6130.