I haven't had any issues transferring a SyncJE license to a new phone - I've done it a half dozen times in my organization without any issues. I just email them and tell them that I have to transfer a license to a new device, provide the license info, and ask they that they release it. I'm then free to register it to a new device. I think they also have a mechanism to let you release licenses, but I don't use it.
All that said, I have not been able to get the SyncJE client to work reliably with the 8350i. We use FirstClass
in our organization and it randomly deletes events, moves events, etc. It worked pretty well with the 7100i, but not with the 8350i. Nexthaus has not been very responsive to the problem.