Dialer App with Rewarded video credit system

The app is 2 pages (+ login page) Page one: Dial pad showing the credit and the cost per min and remaining minutes + control the call when the user exceed the limit page two: Option for the users to buy credit ( in app purchase ) Spin number from 000 to 999 and the user have 200 daily attempts after he got his lucky number he need to watch a video ad for the credit to be added ( hint we need to control the result for the spin number not to be less than 095 or higher than 200 ) Watch video ad to get credit (gives the user random number between 50 and 100 as a gift credit after watching the ad) Invite your friends and earn credit (reword randomly between 5000 and 50 000 credits ) Remarks: 1- There will not be much work on the dialer page as we can implement a ready open source project. check (Linphone) 2- login will be optional to the user to login using Facebook/ gmail or to skip In both ways the app will be fully functioning and storing the credit locally 3- We will implement admob + Facebook ads alternative to each other’s 4- Connection to the voip server will be don’t SIP direct connection (no API needed) and for security we will keep the authentication details (IP,username,password) on the database (firebase) 5- the connection details to the server ( IP/ username/ password ) and the cost per min are to be stored on a server ( firebase ) 6- cost per min is to be a variant that I can change later throw the firebase