I upgraded to KitKit and now calls and texts do not come through when I have wifi calling turned on. This doesn't happen every time, but I would say at least once every other day. I'll turn my wifi off and boom, all my text messages will finally come through.
I'm so disappointed. There were wifi issues on 4.3 and T-Mobile waited and waited to release a fix until they could roll out the entire update as 1 package, and now it's even worse.
I've already wiped the phone clean and started from scratch. That didn't solve anything.