App doesn't let you delete your account. It instantly sends sms message to your phone number to create account or change the phone number but it doesn't send you a sms code when you want to delete your account.
Developer reply
Hello, Bruce! Sometimes there might be problem with sending SMS code because of mobile operator 🙌 You can reach out our support team to help with it. Our managers will be glad to help you 💙 Support chat is located in the app "Profile" section, button "Support", "Chat" 📲