Can anyone help....

I have the Draytek 2750vn router, have tried all the settings i can think of but can not get VOIP to work properly.
The problem i have is i go to make a call firstly the ringing tone is not standard and secondly but more import both parties can not hear anything after answering the phone. Just a hiss noise that you get when you know your connected.

Hopefully someone can help

My voip provider is VOIPSTUNT

Also everytime I try make a call the VDSL (UK BT Infinity) connection drops and then reconnects.

I have tried two different providers VOIPSTUNT and VOIPBUSTER

(Update)

More problems arose:

-Minor smell of electrical burning from the router
-Router also started to make a noise which for having no moving parts or no speaker was weird!
-Router started to interfere with telephone line, when telephone was picked up internet disconnected and also dial tone was not clear. (For users thinking its a filter issue - micro filters are not used with VDSL (BT Infinity) BT fit a VDSL plate on top of the master socket which has the necessarily filters, I have read that VDSL micro filters similar to the ADSL ones will be used in the future to aid self-install)
-And then my internet would not work at all in the end with this Dreytek router

Ended up being a Faulty router Dabs replaced the router and now everything is working perfect including VOIP

Good to hear! Check Draytek's site for firmware upgrades as they release updates every so often, even on an old 2820n that I use at work.