When you say "I need to direct dial to Iamresponding.com to respond to a call", I'm assuming you mean this:
"Here's how it works: After receiving a dispatch notification through any existing dispatch system, responders either press one button on IamResponding's free apps, or speed dial a pre-programmed toll-free number on any phone. This whole process takes mere seconds, at most" (see http://www.iamresponding.com/v3/Pages/Learn.aspx?contentID=2).
So you can either download the Android app from the Google Play store and follow these directions for using the app from IamResponding: http://www.iamresponding.com/v3/articles/AndroidAppQuickStartGuide.pdf
Or you can set up speed dial to IamResponding's toll-free number using this guide: http://webcazine.com/13405/android-5-0-lollipop-how-to-setup-and-use-speed-dial/
If this isn't what you meant by "direct dial" please let me know.