You just need to reinstall Plivo, so to go quickly and not install everything I will advice you to run the following as root :
cd /usr/src/
bash plivo_install.sh /usr/share/plivo
awk 'NR==12{print "EXTRA_FS_VARS = variable_user_context,Channel-Read-Codec-Bit-Rate,variable_plivo_answer_url,variable_plivo_app,variable_direction,variable_endpoint_disposition,variable_hangup_cause,variable_hangup_cause_q850,variable_duration,variable_billsec,variable_progresssec,variable_answersec,variable_waitsec,variable_mduration,variable_billmsec,variable_progressmsec,variable_answermsec,variable_waitmsec,variable_progress_mediamsec,variable_call_uuid,variable_origination_caller_id_number,variable_caller_id,variable_answer_epoch,variable_answer_uepoch"}1' /usr/share/plivo/etc/plivo/default.conf > /tmp/default.conf
mv /tmp/default.conf /usr/share/plivo/etc/plivo/default.conf
/etc/init.d/plivo stop
/etc/init.d/plivocache stop
/etc/init.d/plivo start
/etc/init.d/plivocache start