duplicitous

marked by deliberate deceptiveness especially by pretending one set of feelings and acting under the influence of another; "she was a deceitful scheming little thing"- Israel Zangwill; "a double-dealing double agent"; "a double-faced infernal traitor

The duplicitous salesman sold the sculpture to someone else even though he had promised to sell it to us.

The duplicitous salesman sold the sculpture to someone else even though he had promised to sell it to us.