Ah found it IMessage and FaceTime activation showed up unsuccessful after the update ! Switching them back on made it work and I see a new option inside FaceTime settings : iPhone cellular calls !
Go to the Jailbreak Wizard and try to restored the OS to an earlier version. Jailbreak from there. I'm not sure if it will work for I do recall reading something about the OS not being signed anymore..but it may work if you have your phone on Airplane mode.