Depends on when you bought the system if you have to pay for upgrades or not.
When the 3300 first came out you didn't need to.
Now you need to have Mitel's Software assurance.
The older systems have been Grandfathered in.
There are two SIP licenses available for the 3300. Station and Trunk. If you want to connect to a PBX you need a SIP trunk license. One for each connection you need. If you want SIP phones/softphones, you need a SIP station licenses for each one.
Yes. I still work for SunTel in the remote services center. Joyfully maintaining Mitel products since 1992.
Ralph
www.Suntel.com