If phone has no signal can replacing the charging port fix it?

Firstly does the phone still display an IMEI number and modem firmware in settings > general > about phone?

If not, the baseband chip needs to be diagnosed on the logic board. It's a micro soldering job to fix it (replacing it isn't an option as that will end in disaster).

Is this a phone where you bought it off the internet, it worked from a few weeks to a month and it stopped working? If yes, check general > about phone > first text field under phone name I think and it should be tappable, it may say phone not allowed meaning the IMEI number of the phone has been blocked (happens on phones where they have been reported stolen or the owner did not finish paying off the contract for the phone).