Changed charger port now no cell coverage

It seems like you got an lightning-assembly that is disfunctional, or have problems. As far as i know there are antenna on the buttom(On lightning-assembly) and on the top of the phone. Getting spare-parts for iPhone is harder than you think, because the quality between the spare-parts producers are very different. I would recommend you to order an new lightning-assembly from another seller and try again.

You could also try to reassemble to your old lightning-assembly and see if it makes a differnce.

I also have this problem after I changed the Lightning assembly as described on iFixit. The phone now charges great, but the Settings > Battery shows that "No Cell Coverage" is hogging 30-40% of the battery. The phone will run through its entire charge from 100% to auto power off in about 8 hours, just sitting on a table not being used.

Often "No Service" appears in the top left of the display, or "Verizon" either with either 0, 1, 2 dots or no dot display at all in the meter. It also occasionally displays "Extended". My wife has the same model phone, and none of this happens to her and her battery lasts 24 to 36 hours on a charge. The phones are the same age to the day.

I've tried "Reset Network Settings", hard boot by holding the Power and Home buttons, removing and reinserting the SIM card with the phone both powered down and hot. All done several times, but the battery still drains like crazy.

I suspect there is something wrong with the antenna connection somewhere. When I replaced the Lightning connector assembly, I didn't remove the screen like in steps 13 to 19. Instead I just had the screen open 90 degrees with the connectors still attached. Other than the battery drain issue, the phone functions fine.