I use Euphony as do my friends and family,and some small businesses i know. None of them have ever been billed twice to my knowledge.
In fact if they billed me twice for my calls i still wouldnt be paying anything because their free in my inclusive call package which works out at less then a £1 a week.
As NGMS ghost points out they use a normal geo number,and their customer service people,who have always been helpful to me are based in Basingstoke. Calls to it are FREE from my call package.
They havent followed BT or Talk Talk like sheep.On chargeable calls they still operate the min call charge system with second billing. No connection charge or minute billing for them.They even still have the peak charging band of 8am to 6pm,unlike other providers.
I also use 18185 in conjunction with Euphony for cheaper mobile,and ngn calls.
The only people that might benefit from using Vonage are broadband only cable customers.
But bear these facts in mind
Theirs an activation Fee of £9.99
Then theirs the expensive NGN and UK mobile rates.
Also the dear Intl Rates to non free Intl Destinations.
The recovery fee "If you accept a special offer or other promotion, such as a free month of service, a rebate or other incentive, there may be a term commitment associated with the benefit you accepted. The commitment period will be disclosed as part of the promotion. If you terminate service prior to the end of the commitment period, you agree to pay Vonage a recovery fee for the promotion/special offer you accepted. Recovery fees are cumulative and in addition to any other charges or fees you may owe Vonage. Each recovery fee is an amount equal to the difference between the price you paid and the regular price of the goods or service at the time you accepted the promotion/special offer"
You cant port your number.
Potential problems with 999 calls.
You cant pay by d/d, card only is the order of the day.