Xperia Z C6603 Network Problems

[teosSony1]

So I bought a refurbished Xperia Z (Android 4.4.4 KitKat) a couple of days ago. I put my 4G sim card in and i saw only the "E" sign on top. I have tried everything i have read in this forum, but i can't update my Xperia Z via PCC, or via the phone itself, or repair the problem using anything else. Please help, this is driving me crazy. (And sorry for any spelling mistakes, english is not my native language)

[teosSony1]

Hey man check your PM

[PadreWalas]

I had the network problem in my xperia device after updating to lollipo 5.1, i contacted with my carrier but it seems the problem is belong  to my phone. Becouse when i use same sim card to other phone it works good. When i choose to use only WCDMA i lost the netwok at all and phone tell me no service. I only capable of using 2g network

[teosSony1]

You have my same problem buddy, but I also can't update to Lollipop in any way

[PadreWalas]

if you check network bands btn z6602/3  there is big different, bt i believe sony can fix this only there is delaying

[teosSony1]

I think the people I got the phone from installed the C6603 software in a C6602 model, because I checked my IMEI and it was that of a C6602 and I no LTE bands show up in the phone's service menu, and probably this also messed-up the phone so much

[Latifraza]

I m having network connect issue after 8 months of purchase c6603 since then I m utilize this phone over wifi connection only Pls advice signals are ON / OFF frequently... Or sometimes not at all. Serial No of phone iscb5a1uu8cn Pls advice