Was just about ask the same question. When I am at home I have to have wifi calling ubunt ROM has it and it works better than the wifi does with tmobile factory rom. Why? I don't know?? The only thing I have found wrong with the UD4 is facebook. Which kinda sucks but they say you can delete it and just download the Facebook fb app But that is why I am at Android central today trying to figure out a way to delete it. I have used esfile manager and another program I can look at the app but it won't let me read or write, etc ---protected.
So I am tard proofing myself and reading more info there are more out there just haven't tried them.
I will start a thread!