SMS Credits are required for:

SMS Appointment communications (confirmations, reminders etc)
Direct Messages
Smart Forms
Security Verification for Online Booking
2FA

Only site administrators are able to purchase text credits. To do so:

Go to Settings -> Account
Click on Buy More next to the SMS counter
Choose which bundle you'd like
Follow the payment instructions on screen
Once the payment has been successfully processed, you will see a green banner on screen advising that the transaction has been successful and the SMS counter will be updated with your new total.

Updated on: 25 / 11 / 2020