Yes you can change it, refer the below docs, where phone registration issue has been resolved by changing the sip port to 5065, when both the 5060/5061 were in use.
http://www.cisco.com/c/en/us/support/docs/unified-communications/expressway/118798-technote-cucm-00.html#anc14
http://www.cisco.com/c/dam/en/us/td/docs/telepresence/infrastructure/vcs/config_guide/X8-5/Mobile-Remote-Access-via-VCS-Deployment-Guide-X8-5.pdf
Venkatesh.
-Do rate helpful posts.