In this tutorial, we learn how to use Twilio's Programmable Messaging API and the Google Sheets API to send payment reminders to customers listed in a Google Sheet. We create a custom menu in the Google Sheet that allows users to input their Twilio credentials securely. The script then uses these credentials to programmatically send SMS reminders when a customer's payment is past due or coming up. Users can also choose to send notifications based on a date range, ensuring customers receive timely payment reminders.