This video shows you the procedure of changing the port on which basic asterisk listens. Hold good for vicidial, freepbx, etc.,
1. netstat -an | grep 5060
2. vi /etc/asterisk/sip.conf
3. change the value of bindport to port of your choice
4. save the sip.conf file and exit
5. go to asterisk cli by command asterisk -rvvv
6. sip reload command to make the changes come in effect
7. port is changed you can verify by netstat -an | grep port