play (one) false
old-fashioned To deceive one; to cheat or swindle one. I insisted that they offer something as a collateral before we entered the deal, lest they play us false with their offer. The rogue had been playing the old lady false for nearly a year, preying on her trusting nature to bilk her out of her fortune.
play someone false
prove treacherous or deceitful towards someone; let someone down.