hello

i tried to use nibblebill, here is my configuration:

User Directory:
<include>
<user id="3001">
    <params>
      <param name="password" value="1234"/>
    </params>
    <variables>
      <variable name="toll_allow" value="domestic,international,local"/>
      <variable name="user_context" value="default"/>
      <variable name="nibble_account" value="3001"/>
    </variables>
</user>
</include>

Dialplan:
<include>
<extension name="Test">
   <condition field="destination_number" expression="880">
    <action application="set" data="nibble_rate=0.035"/>
    <action application="set" data="$${nibble_account}"/>
    <action application="bridge" data="sofia/gateway/asterisk/${destination_number}"/>
   </condition>
</extension>

I got following error

2011-09-16 17:18:36.866801 [DEBUG] mod_dptools.c:1167 sofia/external/3001@192.168.7.21 SET [nibble_rate]=[0.035]
EXECUTE sofia/external/3001@192.168.7.21 set()
2011-09-16 17:18:36.866801 [ERR] mod_dptools.c:1145 No variable name specified.

can anyone help me to find the issue, i follwed the Mod_nibblebill wiki Single Rate for all users section.

Regards
shaon