I am trying to find the newest OS I can install on my curve. I have found a couple of newer ones, but they are not cooperating with me. I did change mine from 4.3 to 18.104.22.168 at the end of last year.
Hopefully the new upgrade will help with the calls. Sometimes, I people can't understand what I am saying on the phone. If I resay it, then it may be clear. They ask what did I do, and I say nothing different.