It is my understanding the the Dial phone script step does work in FM Go. This step originally only worked with Dial Up modems back in days of much older technology and had pretty much fallen out of any usefulness until FM Go resurrected it.
You may need to strip out any non numeric characters from the field before it works, however--I seem to remember a post to that effect anyway...
Here's a script from the Contact Starter Solution, iPhone Layout, on a button using the Dial Phone script step (no dialog)
Filter ( Contacts::Work Phone ; "1234567890,+" )