Default [Q] Samsung Galaxy S4 L720 shows Unknown Baseband, IMEI, Software Version and MEID

Hello,

I have a sprint Samsung galaxy s4 L720, unrooted on stock 4.3 baseband version L720VPUAMDC, the problem is that now it shows baseband, software version and IMEI as unknown and also it has an X up in the coverage bars so im unable to make or receive calls. I've never tried to root it or to change it's software. also on few occasions the info about IMEI and baseband comes back and I can make calls again but it just goes back to unknown after a while. also I've tried to reinstall the software and made several factory resets. I just don't know what can I do anymore.

help will be appreciated

thanks.