I have a customer who was running asterisk and updated the phone's firmware to SIP via tftpd32 with the firmwares downloaded from Cisco.
My sales colleagues pitched the CUCM idea and he is finally shifting to it. The problem that I am facing is that I can't get the phones to revert back to SCCP. I tried to manually do it from Tftpd32 using a modified gkdefault.cfg, tried erasing the configuration and registering it with CUCM and under SCCP, tried auto registration after erasing the configuration to no avail. The phone seems to be stuck to SIP. There was a single phone that was reverted to SCCP according to my team member but he still isn't sure about how it happened since he converted it back to sip to check the process again and now it's stuck back to SIP.
I would highly appreciate it if someone could guide me as to how to perform this conversion procedure.
The details are as follow,
SIP firmware rev, 8.0.1 (060412A)
I have a service contract company login so download firmwares is not an issue.