G935F changed IMEI but not work

Finally I managed to change the IMEI of my phone.*#06# show the IMEI changed.
I have installed a firmware NO BRAND and inserted different IMEI, one taken on the net for my g935F and others coming from different apk installed and found on GooglePlay.
But the result is’ always the same: only emergency calls and no recording on my carrier’s network.
What can you suggest me? What the hell more control over the IMEI?