I just discovered if you turn off the "Enhanced 4G LTE mode" under Mobile network settings, you will get rid of the "service unreachable" and your calls, message and data will all work on version wireless network......Outstanding...…..with the two sims, I now have a T-Mobile GSM line and a Verizon CDMA line on one device......
Thanks for posting this. I've seen where you need to have the CDMA sim in slot 1 in order to get things to work correctly. I have a 3rd party CDMA sim which I (supposed to get to work correctly) I will activate on a known Verizon friendly android (Samsung Galaxy S5) then transfer to the ATOM. Will add to this thread at some point.
Please try to give a substantial answer. If you wanted to comment on the question or answer, just use the commenting tool. Please remember that you can always revise your answers - no need to answer the same question twice. Also, please don't forget to vote - it really helps to select the best questions and answers!