Do I have to return the phone call from family child services?

Nobody can force you to return the call, but be prepared for the adverse consequences if you do not return the call. Be smart and meet with an attorney before you return the call. Know your rights. Know how best to handle the situation.

I'm not thinking of any advantage to you in not returning the call. If she left and is seeking child support, the papers will be served on you, not resolved by a phone call. If you think the call relates to allegations of misconduct by you, engage counsel and have counsel make the call.