This is design for chat, audio, video (app to app calls) and to landline/mobile no. We want to have a simple but effective UI (with not a lot of jazzy graphics). This app will be mainly used in enterprises. For iOS as well as Android.
3-4 graphics banner that explains the USP/features of app with button at bottom stating "Start app"
Agree to terms and condition (bottom)
Login with barcode icon at bottom
Enter the 4 digit PIN
Timer stating "we will call you in 5.00 mintures"
Did not receive PIN ? Resend PIN
Enter email address
Password or PIN
Sign-up button, skip button
App initialization screen (kind of processing and loading app)
Main screen with menu icon on top left, dialer icon on top right, search icon (list of chats with 2 tabs: Chat and Call (listing all calls), similar to google hangout)
Material design with + on bottom right, when clicked shows: new chat, new call, new group
Detailed chat screen with audio, video call icons on top right, when clicked on name opens the profile screen
Outgoing call screen, incoming call screen
Contacts Screen with list of all and free contacts
Dialer screen with dial button 0,1,2,3,4,5,6,7,8,9 and few other options on the screen
Display balance on top right, plus button on bottom right that opens contacts
After number is keyed in that show the rate for this call or state that it will be free call
Invite by email/SMS screen
Share in social media site
Note: No of screen increase or decrease by 2 - 3.