Press *69 on the phone immediately after you receive the call,an

*69 is a call back function. It is a service package provide by the phone company and charge per use. If you don't have the service, you can call police and they will check it for you.

FBI官员表示，如果家中的固定话机收到不明勒索电话，可拨打“*69”查询对方号码，如果是手机接到该类电话，可立即挂断，并拨打“*57”，然后再挂断，电话公司会自动记录来电号码。