I tried to use official Clickatell plugin for 3.9 but seems fail. After research, I think the reason is Clickatell is no more support SOAP service. It has moved to new platform in 2016. Configuration like API Id is no more in use. format to call the API is like https://platform.clickatell.com/messages/http/send?apiKey=xxxxxxxxxxxxxxxx==&to=xxxxxxxxxxx&content=Test+message+text&from=xxxxxxxxxxx