WHMCS plugin for SMS notification and OTP
WHMCS is an all-in-one client management, billing & support solution for online businesses. Handling everything from signup to termination, WHMCS is a powerful automation & support tool.
For WHMCS version 7.6.x & 7.7.1: https://www.whmcsservices.com/msg91.php
For WHMCS version 6.2 to 7.4: https://marketplace.whmcs.com/product/1118
For any further help, you can contact us at firstname.lastname@example.org.