Now I see...
You never SEND your command to the service... (And it should be GET and not POST I think)...
Here is the SP...
CREATE PROC Hello
AS
DECLARE @obj AS INT
DECLARE @Uri AS NVARCHAR(MAX)
DECLARE @Response AS BIT
SET @Uri = 'http://MY IP IS HERE :9671/MyWebService.asmx/HelloWorld'
EXEC sp_OACreate 'MSXML2.ServerXMLHttp.3.0', @obj OUT
EXEC sp_OAMethod @obj, 'open', NULL, 'POST', @Uri, false
EXEC sp_OAMethod @obj, 'send'
EXEC sp_OAGetProperty @obj, 'ResponseText', @Response OUTPUT
SELECT @Response [response]
EXEC sp_OADestroy @obj
RETURN