Hello,
Do you have sip peering or registered trunk service? does do you have sip ports (mainly UDP 5060) opened in your region or not? do you have static public IP address on your Cisco router acting as CUCME or not? your phone does not necessarily need to have sip firmware as it could work on regular SCCP firmware, I can do this project quite fast but I added 7 days because I am not sure about your network topology. I will also need to check what codecs are supported by your sip trunk provider.
I have active cisco CCVP, CCNP, and CCIP certifications and have been in this field for this field for more than 11 years but I am new to free lancer website as I created an account but did not actually use it.
Thanks
Iyad