If you have just started using the app after a subscription:
- There is a burger menu on the top left side on the home screen (Messages).
- On tap on the same will give you various options to change.
In case you are on the dial pad screen, please tap the back button on the top left, and you will be navigated back to the Messages screen. And once on Messages, you can follow the above steps.
You will find relevant options on the menu screen - such as Available Credits, Buy Credits, Voicemails, Blocked Numbers etc.