If you get the message that the number you called back is out of service that is a red flag for you never to answer any calls from that number. They are scammers and will attempt to get money from you for illegal reasons. Rule of thumb in my office and home is Do not ever answer any out of state calls, or unidentified callers. Let them waste their time not yours. If they really need to speak to you they can and will leave a message on your answering machine. Then it is up to you if you want to call them back or not. If they don't leave a message, you will be 99.9% sure they are out to take you for what they can and do so rudely.
Too bad something can't be done..phone my house number and my cell every day! I answered a couple of times, no one there, never leave voice mails and once I called the number back..not in service. Area code here is 306..Canada