sending a http request in webPage but prevent opening the page

there is a sms service that can send sms only with a http request. like this: http://domain/SendMessage.ashx?user=[user]&pass=[pass]&lineNo=[lineNo]&to=[to]&text=[text]

if i open this webPage in my webSite , the user can see the user and pass. i want to send this http request but in background (the user should not see the address) and no new tab opened , nothing changes but in background this http request become sent.