I have the Nexus 7 2013 LTE in the UK with the carrier "3". I have installed CM 11 and I can send and receive SMS messages as with any normal phone. The dialer application however shows an error message "Voice calling not supported".It seems like the carriers play a big role in blocking gsm calls for you, have you had someone test it on a european network? They are often way more liberal and don't have many of the restrictions the US carriers have
After reading quite a few posts on the subject of making regular phone calls on the Nexus 7 LTE, I cannot understand the difference between SMS and voice calls - I would have thought that either you get both or none.
When I messed with the IMEI on my other phone, a Zopo300, my carrier "3" refused to allow connection, I was getting no signal at all. On the Nexus 7 I get full signal and can send and receive SMS .
We just need to find what's missing. Can it be simply the lack of a speaker - is that something that causes the error "voice calling not supported" ?