There is a TEENY TINY inductor on the motherboard which is apparently very easy to knock loose of the soldering and therefore breaks the antenna circuit if is dislodged, I would look at that if a software solution is not helping. Most of us doing first time repairs were entirely unaware we'd lost it most likely when we first removed the motherboard's last screw under the "Do not remove" warning tape. I had no idea why my new screen worked so beautifully but I had a whole new problem of "no service"! I tried everything and found no solution until this (thankfully someone figured out what no one else had)
Check for this component either missing or loose and/or damage to circuit traces in this area. Also check that the dock connector piece hasn't come apart at the seam and lost the spring loaded pin which is supposed to contact a small pad on the motherboard - too tight screws or the wrong screw can cause the board to bend just enough to break that contact because it lifts away from the pin also.