HTTP POST method changing to HTTP GET when it receives on the server

Question

I am using ASP.net. I have a web page that receives the data from ay POST method call ( created that as a service). However my client is sending the data in POST method but when it comes to our server its changing to GET method call. so the POST data is getting lost. How do we enforce the settings "Redirect with the original HTTP method instead of the default behavior of redirecting with GET." while sending data in POST method? .

From Postman if I select this option I am receiving the data as is. but do not have an idea how do I enforce from the client code while calling our service .

this is happening only when calling the service using "https". the same service i deployed in a server that uses "http" is getting the POST data as is there is no change in the ASP.net code.

your help in this is highly appreciated. thank you.