Of course, check your action first. It could be misspelled or mistyped.
What can happen is that your BizTalk works fine with a WCF web service,
but then you move the WCF service to a different machine and get the error below.
Apparently, this only happens when the different machine is in a different domain.
{!{code}!}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{!{/code}!}
Add the code below to the web.config for your WCF web service.
{!{code}!}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{!{/code}!}