Link2Voip's numbers are down.
Inum +8835100-7xxxxxxx are also down as they were allocated to Gizmo Project, which Google closed earlier this year.
Have you tried sip:<number>@sipbroker.com?
(e.g. *67312345678@sipbroker.com to call
12345678@ekiga.net )
If you want a SIP address that gives the interactive service, you could try:
sip:317100055@eurovoice.ro (Romania)
sip:43720732782@pbx.tms-it.net (Austria)
Indeed, try some access numbers on the PSTN Number page into enumquery.com and see what SIP addresses you get out.