Error "Symfony \ Component \ HttpKernel \ Exception \ MethodNotAllowedHttpException" in contact us form

I'm following this tutorial link to make the functional contact us form for my web, not for just localhost. But first I want to try this on my localhost, then will set the email address, on which I want the e-mails to be sent.

The route for my contact us form is working fine as I'm able to see the form at following url:

localhost/contactUs

But when I hit the send message button I get an error of

Symfony \ Component \ HttpKernel \ Exception \ MethodNotAllowedHttpException

and the url changes to this, but with the above error

localhost/contact_request

What am'I missing here? Should I have to make another view for contact_request, if yes then where should I make it?

Please help me out I have spent whole one day on this but didn't get any success.

Thank you in advance.