unsell

verb

1. (transitive)To cause to appear less attractive to consumers or adherents.

   “Politicians will try to unsell the public on its conviction of rearmament.”

   “At the same time, every effort to unsell something may also be viewed as an effort to sell something else. Those who attempt to unsell cigarette smoking are attempting to sell health...”

   “After the meeting Bob grabbed me by the ear and told me, "Once you make the sale, shut up and don't unsell it."”