Extensions Dialing Itself

hi guys , have been using elastix for really long but recently starnge thing is happening, my extensions are calling themselves some random numbers due to which my voip credits keep getting epired. please hel me
here is the cdr sampale

2012-04-05 21:20:35 1333675235.162 SIP 2014 Busy 00972546914969 SIP BUSY 00:03
2012-04-05 21:20:33 1333675233.160 SIP 2014 Busy 972546914969 SIP BUSY 00:20
2012-04-05 21:20:31 1333675231.158 SIP 2014 Busy 011972546914969 SIP BUSY 00:25
2012-04-05 21:20:11 1333675211.156 SIP 2014 Congestion 972546914969 SIP FAILED 00:09
2012-04-05 21:20:09 1333675209.154 SIP 2014 Busy 00972546914969 SIP BUSY 00:05
2012-04-05 21:20:07 1333675207.152 SIP 2014 Congestion 011972546914969 SIP FAILED 00:12
2012-04-05 21:19:33 1333675173.150 SIP 2014 Dial 011972546914969 SIP NO ANSWER 00:50
2012-04-05 21:19:31 1333675171.148 SIP 2014 Congestion 972546914969 SIP FAILED 00:15
2012-04-05 21:19:29 1333675169.146 SIP 2014 Congestion 00972546914969 SIP FAILED 00:15
2012-04-05 21:18:54 1333675134.144 SIP 2014 Busy 011972546914969 SIP BUSY 00:20
2012-04-05 21:18:52 1333675132.142 SIP 2014 Busy 00972546914969 SIP BUSY 00:03
2012-04-05 21:18:48 1333675128.140 SIP 2014 Busy 972546914969 SIP BUSY 00:19
2012-04-05 21:18:04 1333675084.138 SIP 2014 Congestion 011972546914969 SIP FAILED 00:10
2012-04-05 21:18:01 1333675081.136 SIP 2014 Congestion 00972546914969 SIP FAILED 00:10
2012-04-05 21:17:59 1333675079.134 SIP 2014 Congestion 972546914969 SIP FAILED 00:10
2012-04-05 21:17:35 1333675055.132 SIP 2014 Busy 011972546914969 SIP BUSY 00:22
2012-04-05 21:17:31 1333675051.130 SIP 2014 Dial 00972546914969 SIP NO ANSWER 00:25
2012-04-05 21:17:29 1333675049.128 SIP 2014 Busy 972546914969 SIP BUSY 00:20
2012-04-05 21:17:25 1333675045.126 SIP 2014 Busy 00972546914969 SIP BUSY 00:05
2012-04-05 21:16:45 1333675005.124 SIP 2014 Busy 972546914969 SIP BUSY 00:21
2012-04-05 21:16:44 1333675004.122 SIP 2014 Busy 00972546914969 SIP BUSY 00:11
2012-04-05 21:16:36 1333674996.120 SIP 2014 Busy 011972546914969 SIP BUSY 00:35
2012-04-05 21:14:19 1333674859.111 SIP 2014 Congestion 900972598143761 SIP FAILED 00:10

You system has probably been compromised in some way. Is it exposed to the Internet?

yes