Background:
SInce 2002, I have kept a VOIP number with Vonage, one of the first companies in US which had such service. Recently, after their locked adapter refused to work, and bad experience with theirBlackberry dialing application, I decided to consolidate this number to my Broadvoice account (an extra number costs a cent shy of $2 a month.)
Attempts to just close the number through Vonage customer servce were met with "this is another department, let me transfer you" line.
Timeline and Results
nov04: submitted online LNP request to broadvoice - no paper letter to send!
nov05: broadvoice asked for phone service address; replied to them
nov12: notified by Broadvoice about nov17 effective date
nov19: vonage account cancelled automatically after porting to broadvoice completed
Vonage Monthly Customer Count
In my account portal, there was an invoice history; based on that, somebody can reconstruct size of their customer base since company started offiering the service (I was within first 300 customers, it seems.)
Here is the link.