The problem, i m confronting right now, is that

When I make 2 calls simultaneously from 4 phones,it acts like a Conference Call means everyone is listening to everyone,
For Example if cell A calls cell B,AND cell C calls cell D,then cell C can hear the conversation between A and B. and similarly vice verse is happening.

Here is the extension  that i m using to make calls,
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<extension name="local_call">
<condition field="${python(VBTS_DB_Get name|callerid|${destination_number})}" expression="IMSI\d{15}"/>
<condition field="${python(VBTS_DB_Get callerid|name|${username})}" expression="\d{7,10}">
<action application="set" data="target=${python(VBTS_DB_Get name|callerid|${destination_number})}"/>
<action application="set" data="port=${python(VBTS_DB_Get port|callerid|${destination_number})}"/>
<action application="set" data="host=${python(VBTS_DB_Get ipaddr|callerid|${destination_number})}"/>
<action application="set" data="effective_caller_id_number=${python(VBTS_DB_Get callerid|name|${username})}"/>
<action application="set" data="hangup_after_bridge=true"/><action application="set" data="continue_on_fail=true"/>
<action application="bridge" data="sofia/internal/${target}@${host}:${port}"/>
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Does any one has any feedback on this why this is happening.

Thanks in Advance