In order to change your InTouchApp username, please follow the steps given below on InTouchApp installed on phone.
Step 1 - Open InTouchApp on your phone.
Step 2 - Click on your profile on top centre at the screen.
Step 3 - Click on Settings at the top right corner.
Step 4 - Click on Profile (under Manager your account) and you will see the Username listed there.
To Change Username:
Step 5 - Click on Change beside the Username.
Step 6 - Enter your new username and check availability. Click on the Green Tickon the right and it's changed.