[Serusers] problem between UAs

Hi I have few users.. one user can call to another but other can not e. g user - 01551 can call 01331 but 01331 is unable to call 01551 user- 01331 gets message as 404 not found on x-line soft phone here is the ser logs 2969) get_hdr_field: cseq <CSeq>: <16463> <REGISTER> 0(2969) DEBUG: is_maxfwd_present: value = 70 0(2969) end of header reached, state=9 0(2969) parse_headers: flags=256 0(2969) DEBUG: get_hdr_body : content_length=0 0(2969) found end of header 0(2969) find_first_route(): No Route headers found 0(2969) loose_route(): There is no Route HF 0(2969) REGISTER: Authenticating user 0(2969) check_nonce(): comparing [402de230ebd314d08c3f944f8852c57be3deb86c] and [402de230ebd314d08c3f944f8852c57be3deb86c] 0(2969) radius_authorize_sterman(): Success 0(2969) save_rpid(): rpid value is '1234' 0(2969) parse_headers: flags=-1 0(2969) parse_headers: flags=-1 0(2969) check_via_address(202.71.135.212, 202.71.135.212, 0) 0(2969) receive_msg: cleaning up 0(2969) SIP Request: 0(2969) method: <ACK> 0(2969) uri: <sip:01234@sip.net4india.com> 0(2969) version: <SIP/2.0> 0(2969) parse_headers: flags=1 0(2969) Found param type 235, <rport> = <n/a>; state=6 0(2969) Found param type 232, <branch> = <z9hG4bK12F5D0D068764E39AC550A54156063BD>; state=16 0(2969) end of header reached, state=5 0(2969) parse_headers: Via found, flags=1 0(2969) parse_headers: this is the first via 0(2969) After parse_msg... 0(2969) parse_headers: flags=4 0(2969) DEBUG: add_param: tag=d94c2b94918adbff86ad0d1f78fe5d3d.5ec2 0(2969) end of header reached, state=29 0(2969) DEBUG: get_hdr_field: <To> [73]; uri=[sip:01234@sip.net4india.com] 0(2969) DEBUG: to body [<sip:01234@sip.net4india.com>] 0(2969) DEBUG: sl_filter_ACK : local ACK found -> dropping it! 0(2969) receive_msg: cleaning up 0(2969) SIP Request: 0(2969) method: <ACK> 0(2969) uri: <sip:01234@sip.net4india.com> 0(2969) version: <SIP/2.0>