How do change my login (registered) email id / phone number?

If you want to change the registered email id, as of now, there is no provision in the app to change the logged in / registered email id. Nor can it be done from our end. Also, there is no way to logout of the app. 

The only way to have a new email id is to delete the app and reinstall it again. While prompted to login, sign up with the new email id. 

Note:

If you have customized the app, ensure that you have taken a backup, and stored it in cloud, before deleting the app.