It is also possible to use an external web service in the NAV. Microsoft provided this functionality using the inbuilt codeunit 1290: SOAP Web Service Request Mgt.. Here, you can write your own codeunits and call codeunit 1290 to send a request and get a response.
Note
I would recommend that you take a look at https://community.dynamics.com/nav/b/moxie4nav/archive/2015/09/10/call-external-web-service-using-new-cu-1290, which is an interesting way to harvest this functionality.