You will have to use the Adapter Development Kit and an SMPP library, to build your own. There used to be a package named WmCommunicate, but I’m not aware of an out-of-the-box adapter/connector.
ADK - https://documentation.softwareag.com/webmethods/adapters_estandards/Adapters/ADK/adapterdevelopmentkit.htm
Apache SMPP - SMPP :: Apache Camel
SMSLib - https://docs.huihoo.com/smslib/3.5/about.html
Caveat - The libraries that I’ve mentioned above may be outdated, so do look for latest supported versions or alternatives.
KM