asterisk users - Dec 2005 - Sip configuration for make and receive calls

Hi,

I'm having some problems configuring a SIP account from a VOIP service 
provider named voztele.com. I can configure it to make calls or to receive 
calls, but not both :)
Here is my sip.conf, with it, I can make calls, but not receive. If I comment 
all of the user voztele, then I can receive call, but can't make...

[general]
context=default
bindport=5060
bindaddr=0.0.0.0  
set canreinvite=no
register => username:secret@serviceprovider.com/100
externip = my_public_ip
nat=yes
disallow=all
allow=alaw
allow=ulaw
localnet=192.168.1.0/255.255.255.0

[voztele]
type=friend
username=username
fromuser=username
fromdomain=serviceprovider.com
host=serviceprovider.com
secret=secret
nat=yes
qualify=4000
canreinvite=no
reinvite=no
dtmfmode=rfc2833
context=default
insecure=very