Like many people out there - I have had a bad experience with MCI. My personal experience involved three months of daily phone calls to every number I could get a hold of, faxing in complaint letters, copying bills, etc. because I was overcharged $600.00
On several occasions, MCI admitted that they were wrong and it was a mistake, and that I would be getting a refund. Of course the refund would never come.
After I received my third "this is the last time we're saying no" letter I got hold of the FCC. Ten days later I received a credit from MCI. The funny thing is that the day after I received the credit, I received a fourth "this is the last time we're saying no" letter.
What I've learned, and what I want to share with everyone out there is that getting the FCC involved is an easy way to get results. In order to get them involved, you have to have made a reasonable effort to resolve the dispute with your Long Distance Carrier. You should have this well documented. All you need to do is fill out the form at
http://www.fcc.gov/cib/ccformpage.html or call 1-888-CALL-FCC to have your complaint taken over the phone. The FCC will send a copy of the complaint to the LD Carrier (in my case MCI), and then poke a needle in the proper voo-doo doll.
I'm not very familiar with the intricacies of the FCC - but they do hold a great deal of power over every company in the Telephone industry - including the ability to shut down Telephone Companies. When they get involved it doesn't necessarily scare the carrier, but it does make them aware that they have a serious problem and an upset customer.