[CallCentric] Transfer a call on an IP phone

I was trying to transfer a call to another subaccount (extension) on my Polycom 331 phone and it would not work. According to this post (https://www.dslreports.com/forum/r29638803-) the IP phone uses the SIP REFER method to perform this action, but Callcentric does not support the REFER command. Kind of hard to believe that I can't transfer from one extension on Callcentric to another with an IP phone. I don't think the Polycom IP phone can be configured to "bridge" the calls, which would be a pretty crappy solution anyway.