When you receive a phone call and the screen on your phone shows that the number is "unavailable" it is because the person calling you has blocked their information. In most cases, you probably just ignore the call and go about your business. However, when you continue to receive this type of call it can be annoying, especially when the calls come during work, school, or some other time you really don't want the phone to ring unless it is an emergency. The best thing to do is to just block the call. Unfortunately, unless you have a phone number, you cannot do this. Here are a few options for finding the number.
Many phones, even landlines, have the ability to trace a phone call using the code of *57. As soon as the caller disconnects the line, dial *57. If your phone has this capability, you should receive a message telling you the number that just called. It will not always work, but it is worth a try.
Another option when you have a cell phone is to go online and check your phone call records. People do not realize that just because they blocked the number from showing on your screen, it may not block your phone records. You can also contact your phone company and ask for a copy of the calls you received that day. This can be done for landlines as well as cell phones. It may take a few days to get the records, but you should be able to find the number and then block it from calling you again.
Unknown Phone Number Directory
If you have no other option, answer the call and ask who is calling. Generally, they will give you the name of their company. You can then search an unknown phone number public directory to find all the phone numbers associated with that business. This may be the best option as you may find that the company has more than one number and will go through them all trying to reach you.
Do not rely on the "Do Not Call" list to keep telemarketers from calling you. If you have a smartphone, you may want to consider installing an app that will trace these calls for you so you can then block the number. It would be a good idea to then look that number up on a reverse number directory and add any other numbers that company may have to your blocked numbers.