Two calls from Vonage in the past day, both times asking for me by name. Never had sales calls on my number before, I'm very careful who gets my number and always tick marketing material to make sure I don't receive any.

When I asked the first person where he got my number from he hung up. The woman who called the second time stated 'a publically available database', when I asked which one she hung up.

Where do they get these numbers from, plus when I called Vonage back to register a complaint the sales department said I need customer service, and you guessed it, customer service said I need sales - they wouldn't let me register a complaint!

So how do I go about resolving this issue with them?

Does registering with:

http://www.tpsonline.org.uk/tps/

stop sales calls on VoIP lines, in the same way as it does on ordinary landlines?

Thing is I've had the same number for years, so the first sales call in all this time has riled me and I don't want this to be the opening of floodgates so I want to know where they obtained my details.

Why would Vonage sales be calling? I doubt very much the fact that Vonage CS would hang up just because you asked for an explanation. Why would they use a public database when they have you as a customer?
I would ring CS and insist it's their problem as you are an unhappy customer. If it was Vonage making the calls then they should help. If it was not them then you have had your number taken from some other company who you gave your number to most likely.
I have never received a sales call from them in the years I've used them....

I'm not a Vonage customer though, never have been. Doubt all you want, the conversation with Sanjit, the first salesman, went along the lines of -

Phone rings, I answer, pause then I hear ringing twice. When the ringing stops I get -

'Hello, can I speak to (my full name) please?'
'Yes speaking'
'My name is Sanjit I'm calling from Vonage, have you heard about using your broadband internet for the telephone?'
'Yes you're calling a broadband telephone right now with one of your rival companies, I'm not interested, however can you tell me where you got my details from?'
'Okay sir sorry to trouble you'
'Hold on where did you get my' (click)

And that's pretty much the gist of the conversation. I'm not asking you to believe me, I'm presenting it as a statement of events.

Sorry CS wasn't doubting yourself just Vonage...I made the error of assuming you were on Vonage already.
So the answer to your original question is ..I have not bloody idea..

Ah, you're not on Vonage. My earlier reply (Post 2) still applies - have you signed up yet?