[Asterisk-Users] VOIP in Japan using Freebit

[Pikoro]

Has anyone had any experience using a VOIP provider in Japan?

No matter what I try, my REGISTER string kicks back one of 2 errors:
Got SIP response 481 "Call/Transaction Does Not Exist" back from x.x.x.x
or
Got SIP response 400 "Bad Request" back from x.x.x.x

My register string is as follows:
05075034132 at ipphone2.freebit.ne.jp

I have tried the following also:
05075034132:mypass at ipphone2.freebit.ne.jp
05075034132 at ipphone2.freebit.ne.jp/05075034132
05075034132:mypass at ipphone2.freebit.ne.jp/05075034132
myuserid:mypass at ipphone2.freebit.ne.jp

and variations of the above.

Is there any other information I could provide in order to get some help?

I guess another thing I am looking for is a list of possible 
registration strings.. I'll try them all :D

Cheers