In this way, you can send SMS Through Serial port in C#. Still, if you found any problem in sending SMS then you can drop your problem in a comment section.

Bulk Promotional and Transactional SMS Provider
In this way, you can send SMS Through Serial port in C#. Still, if you found any problem in sending SMS then you can drop your problem in a comment section.
Choose reliable and faster web API and also check their support team provides.You can also choose MSG91 API for sending SMS through window application.