Nexus 5 stuck on EDGE , LTE is On but no connection

Search This thread
Hello
I bought my Nexus 5 about a year ago , and everything was fine , suddenly i've been facing some problems with network . The problem is i have EDGE with a small x next to meaning that i have no internet , when i change it to H+ it works but it's so slow "1mbps or 40~100Kb in download" sometimes i get LTE with that small x next to it and no connection keeps loading , and sometimes there's no "x" but still with no connection.
So i thought that the problem is with 3g and 4g wires "black and white " , so i changed them with my friend's wires "he has a nexus 5 too" but it didn't fix the problem . So i went back to stock rom and nothing happened
-Tried different modems nothing happened
-Cleaned the whole motherboard with some cleaning tools nothing happened
-Checked the contacts below the "speaker" cover
-Changed my firend's back cover
-changed the sim , tried my sim in another phone and it was working fine
-changed the network operator
-chcked the APN
-did some secret codes to put it on LTE only and i get no network .
I did everything but i still have this problem
I was reading something in some forums and they said that i have change the network IC ! But i'm not sure about it , i mean if i have "no service" problem i haveto change the IC , but i could make calls and H+ is slow but no EDGE or LTE .