you have marked aspx page method as webmethod but if you need to call this method as web service you need to create asmx web service, wcf web service or other web service API which enable you to call the method as web service.
for testing purpose add web service file to your asp.net project (.asmx file) and include your method, set that page as startup page and run the application. then you can see the service operations and how those service operation soap request created.
check below detailed process of testing web service using fiddle
Tutorial: Using Fiddler to Compose HTTP SOAP Requests to the AppFxWebService.asmx[
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But fiddle is not web service testing tool which I recommend, try soapUI
Test Your ASP.NET WebService using SoapUI[
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