私だったら「He is married. What do you want from him(us)? 」で、わざとらしくPleaseを強調して「Please leave us alone. Don’t call him(us) ever again!」かな。で、最後に「by the way, What is your name?」とか?
Hi, your receptionist has kept calling us and left REALLY uncomfortable messgages. Could you leave her a message that she’d better not flirting around her patients like that?