i just bought this phone in used, but i am getting problem of not registered on network,i am unable to send any sms or doing phone calls,i upgrade the software to marshmallow 6.0,,but problem still there,, i check this phoen IMEI on web @ IMEI.INFO there showing my phone modal number sm-910u instead of sm-910f is there a IMEI problem with my phone or something else ??? need help !!!!!!!!!!!!