Simply let them change their expectations of you via the conversation rather than beating them over the heads with it. Patience is a virtue in this instance.
Had it recently happen to me: in a Chase branch, opening up a business checking account and going through the usual routine, and the banker told me I was preapproved for a business card, and I immediately picked the Ink Cash... she backpedalled a bit and suggested I let her describe the differences, and I simply said restaurants vs. hotels; she stared at me for a few heartbeats, said she'd never had a customer who knew the differences before, and then the entire tone of the conversation changed dramatically: suddenly it was between equals rather than the typical banker / customer relationship I've experienced in the past.
Pretty much all of life works like this I've found personally: if you're showing off, or trying to prove you're the smartest person in the room (and maybe you are, it happens), you generally won't get the same respect vs. simply letting it show through in the course of the social exchange. Virtually all my relationships changed for the better once I figured this out... not certain why it took me so bloody long but for every area an individual is smart or knowledgeable, they're usually stupid or ignorant somewhere else, and I am a social idiot.
