I need to change log in method in an android app which have been developed by a developer whom I hired from freelancer but he is not responding from so long so I need a good android developer who can modify this app and also I want to build a long term bonding because time to time I need many updates on this app and I am finding a good developer because my existing one is lost. This app has OTP based log in method but I want it to replace by mobile number as user ID and PIN based log in method.