Fm Go can connect to files hosted by FileMaker Server or FileMaker Pro (limited to 9 such clients) if you can establish a reliable wireless connection--which depends on your local 3G coverage, you can do this. This will be the simplest way to collate the data gathered by your srevice crews.
Thanks PhilModJunk, so if I don't have to use FM server, how would I make the connection?
Filemaker Server is designed to allow up to 125 connections at one time, or is it 250? In your case it doesn't matter.
Filemaker Pro as noted above can also act as a server for upto 9 connections which is in your ball park.
So, use one computer as a dedicated server using just Pro. Don't let anyone work on it. And only run Filemaker on the computer. Then connect it to the Internet and your local Lan or Wifi network.
The first problem you will encounter is a fixed IP address and you'll need to talk to your internet provider about that.
A handful of problems will rise up and you may need help from an experienced consultant to solve them.
The easiest method is to get an internet host who is really Filemaker serious and upload your file to them and let them worry about the misc details. This probably costs $20-50 a month and is worth it especially when you consider all the things you would have to do to protect your data files: one computer, copy of Filemaker, script a backup, fee for static IP, router, batttery backup (should be one of the big ones that will stay on for an hour)....etc...and learn how to deal with the corrupted file after a serious crash.
Since your are using this for a business you should go the safest and most reliable route and even look for the best host, not the cheapest.