currently all our users got 3 digit internal extension numbers and I wanted to change to 4 digit.  I have changed on phone settings and internal calls between extensions and outgoing calls are working but incoming calls are not landing on correct DID...

8821 firmware update to SIP8821.11.0-4SR2-15. after the update phones are not registering to CUCM, please help

any recommended tool to remote the IP phones which are registered with Cisco Call Manager Express(CME).