asterisk users - Apr 2011 - Asterisk modifies from header

Hi,
	I have configured few users in my system with '-' E.g. 1000-1001,
1000-1002 etc..
	I am successfully able to registered as 1000-1001 and dials number
937575346. The other end sees 10001001 (missing '-') as a caller.
	I did verified in the packet capture surprisingly it is asterisk
which did this.
	So, here calling is not a problem and my extensions.conf is bare
simple.
	Can anybody point me to where should I look into?

Thanks,
Niraj