You could have been really polite and helpfull. Tell them that you have to get information from your cowworker who deals with this and will call back right after you got it or that you need some paper trail (e. g. FAX, letter). That often brings the call to a sudden end. It has the advantage of not having been rude to a potential customer.
In our company customers sometimes call the wrong person and they always accept when you tell them that you are going to relay their request to the person in charge. The callers with dubious offers usually hurry to end the call promising they will call again (none of them actually kept the promise).