Pocket Radio doesn't have accounts with names or email addresses. The server only knows the channels and callsigns you use. Deleting your data removes all of it.
Nothing is kept afterwards. Voice was never stored, and the server's logs never contained anything identifying you. Your settings and channel list on the phone are removed when you uninstall the app.
Email support@pocketradio.net with the subject "Delete my data". Because there's no name or email linked to your data, tell us the callsign and channel names you used so we can find it. We'll delete it within 30 days and confirm by email.