windows application to test api

I'm looking into integrating some api in my application, but before deciding on the api I would like to test it to make sure it works right for my needs, so I would like to create a windows based application so I can run tests to see the speed and how it functions.

The api i'm looking to use is from https://sms-gateway.app/ look at help...

I need s simple interface where I can type mobile number where to send the sms and a message