diff --git a/asterisk/conf/mobile/extensions.conf b/asterisk/conf/mobile/extensions.conf
index b86a64f..0a6b6cb 100644
--- a/asterisk/conf/mobile/extensions.conf
+++ b/asterisk/conf/mobile/extensions.conf
@@ -9,6 +9,9 @@ QUEUE_ONE = queue-one
 ; Voicemail address (configured in voicemail.conf)
 VOICEMAIL_BOX = 1000@default
 
+; Trunk numbers.
+TRUNK_ONE_CID = +447123456789
+
 ; First, some safeguards against abuse of the built-in contexts.
 [default]
 exten => s,1,Verbose(1, "info: ${CALLERID(num)} was passed to default")
@@ -46,7 +49,7 @@ exten = 1571,1,Verbose(1, "info: ${CALLERID(num)} dialed voicemail")
  same = n,Hangup()
 
 [from-quectel0]
-exten => s,1,Queue(${QUEUE_ONE},nr,,,50)
+exten => ${TRUNK_ONE_CID},1,Queue(${QUEUE_ONE},nr,,,50)
  same => n,Answer(500)
  same => n,Voicemail(${VOICEMAIL_BOX},su)
  same => n,Hangup()