Helo, i was wondering if anyone could successfully login with a SIP phone (hardware or software) to any of these sites provided by the german Betamax service that unfortunatly doesn't have any support forums
(voipbuster.com,
lowratevoip.com)
or voipdiscount.com

In all it says that .. the users can use SIP registration without having to use the software app that they are providing...

eg:http://lowratevoip.com/en/sipp.html

I have tested with SjPhone and then with a wifi SIP/GSM dual phone called Tc-300 from T-COM

I've put the configuration that they are saying but i always get Authentification failuire
Note that i'm behind a NAT always..(i have forwarded the ports to the local Ip from the router the 5060..but still nothing)..
Any ideeas , or where to find a cheap service like this?
Thanks!