It means just what they say. This must be a cell phone, since it has a coverage area. That would be the area code of their normal cell phone number. Otherwise you can't reach them until they come back. Keeping this in view, what does the person you are trying to reach is unavailable?
“You have reached J.P. Morgan Chase; the person you are trying to reach is unavailable to take your call. It'll sound more like, “You may try to reach this person by email or on their cell phone.” The implied message is that the caller is an insider or has the email or cell phone number already.
Furthermore, what does it mean the number you have called is not assigned? It means that the number you are attempting to call has not been fully configured to send the call anywhere. For example on a Voice over IP system the number you call must be assigned to ring somewhere: To a phone (VoIP) device. To a Voicemail. To an External phone number.
Also know, what is it called when you call a number and it says not in service?
When you called back, you may have been listening to their recording of a phone company message stating the number has been disconnected or is no longer in service. They tracked that you called back in and the robocaller now knows it is a good number and keeps trying to get you on the line.
What happens if you text a number no longer in service?
If the recipient changed their number, you can keep sending messages to the old number, but they will not be received by the same person. If the number has been reassigned, then someone else would receive your message.
Related Question Answers
How do you know if a number is no longer in service?
Listen for the rings. If the phone rings numerous times, but goes to voicemail, that may mean the phone number is still in service. If the number is not in service, when you call it may ring once or twice but you will then get an automated message. What does it say when you text a number no longer in service?
Generic message adopted It reads as follows: We're sorry; you have reached a number that has been disconnected or is no longer in service. If you feel you have reached this recording in error, please check the number and try your call again. Why you should not answer unknown calls?
Plus, even just answering this four-word phrase phone scammers use with a one-word reply could let them steal your money without asking for more information. In general, you're better off ignoring an unknown number and forgetting about it, says Velasquez. “Any important news will be left in your voicemail,” she says. Should you call someone back if they don't leave a message?
It's better to let them call you back. The original caller is the lead person when it comes to this call. If you're leaving a message, say that it's a friendship call, nothing urgent, and that she can call you back at her convenience. What happens when you call a spam number?
If you call them, the spammer can find out if that phone number is owned by an actual person. The spammer can also easily fake the same area code as you, and set up a clever social engineering trick that may involve you thinking with the wrong head. What happens when you call number that blocked you?
If an Android user has blocked you, Lavelle says, “your text messages will go through as usual; they just won't be delivered to the Android user.” It's the same as an iPhone, but without the “delivered” notification (or lack thereof) to clue you in. Will my phone be hacked if I answer an unknown call?
Your phone can be hacked by any hacker just knowing your phone number. You don't have to answer anything. They have your number and then they can listen to your phone calls read your texts and even find your location. But yes whether you accept a call or not they only just need the phone number. Why would someone use an unallocated number?
Why would a person use an unallocated phone number as a business number? Telephone companies do this because they receive a portion of he call cost as payment when they transit a call — allow their switch fabric to be used to connect a call from point A o point B. What are unassigned phone numbers?
Unassigned numbers are phone numbers that are valid for your organization but are not assigned to a user or a phone. The unassigned number table can include both assigned and unassigned numbers, but it is invoked only when a caller dials a number that is not currently assigned. Why do I get calls from numbers that are not in service?
This is a common digital line from the phone company that provides 24 telephone lines that are only used for outbound calls from the business. When you called back, you may have been listening to their recording of a phone company message stating the number has been disconnected or is no longer in service. What does it mean when a disconnected number calls you?
When you call the number it's usually a disconnected number, so that when you call back you don't get a real person, you get the "that number has been disconnected" recording. They don't "have your cell phone number" - they've called every number in the region. What does an unassigned area code mean?
Area code listing Calls from an unassigned area code are likely a telemarketer spoofing the area code and phone number to prevent the call from being blocked or ignored. What does it mean when a number calls you and you call back and its disconnected?
When you call the number it's usually a disconnected number, so that when you call back you don't get a real person, you get the "that number has been disconnected" recording. They don't "have your cell phone number" - they've called every number in the region. 
