Contact list is updated once in a day, so if your friend register his/her phone number after your registration, your friend’s name will not be displayed in your contact list. But don’t worry, your friend name will be displayed tomorrow in your contact list. Tip!!! unregister your phone number and re-register your phone number, then you can see your friends right now.
Your friend’s phone number should exist in your contact app of iphone, and should exactly match with phone number that he/she register to server.
Of cause your friend should install Awesome Calendar or Awesome Calendar Lite(free version) in his/her iphone. Ask your friends to install Awesome Calendar and test it!!!