PhoneTray shows Unavailable or blank instead of the caller's number when your modem doesn't detect caller ID on incoming call. If PhoneTray shows Unavailable / blank for almost all incoming calls, most likely your modem cannot detect Caller ID on your phone line and you will need a new modem. We have a list of recommended modems at www.phonetray.com/modem. New Hiro model H50228 (the second modem listed) has very reliable Caller ID detection and works very well with PhoneTray. Please give it a try.
Normally you should see almost all calls with a correct caller's number and a few Unavailable / blank calls from time to time. Some telemarketers use blank Caller ID to hide their number. To block such calls please check "Block calls with empty caller's number" option on the Privacy - Call Blocking screen: