For iPhone, open the app > click on the 3 horizontal dots at the bottom right of your screen > My Profile > scroll down > Delete Account.

For Android, open the app > click on the 3 horizontal lines at the top left of your screen > My Profile > click on the 3 vertical dots at the top right of your screen > Delete Account.

Please note that deleting your account means erasing all data you ever recorded with the Ava. There is no way to recover that data once your account is deleted.