Has anyone had any success using the voip.co.uk service in conjunction
with a NTL residential Internet account?

I am using a Grandstream HandyTone-486 ATA which connects ok to the
voip.co.uk SIP server. I am able to receive calls from PSTN lines but
when I try to call a telephone number, I hear the line ringing and
then when the person I am calling picks up their phone, the line
immediately drops. It has been like this ever since I signed up last
weekend.

I have heard only positive things so far about voip.co.uk on this and
other forums so am beginning to wonder if it is anything to do with my
NTL Internet connection. Does anyone know if NTL are blocking any
ports which could be causing my problem. Or could anyone suggest any
other possible causes?

Many thanks,

Steve