my sim wont work in my phone but works in others

I have a ZTE blade G LUX and my sim just stopped working in my phone.
other sims work fine in it and my sim works in other phones (weird I know)
have been on the phone to zte who are blaming yatango (carrier) and yatango who are blaming ZTE
when my sim is in my phone it says emergency calls only but the phone recognizes the sim
have turned it off and on, done factory reset, checked message center number, to no avail
please help