I experienced the same problem with my Samsung S2. I had destroyed the charging port by being careless when charging it which meant my phone would not charge at all; although if I was lucky I would get about 10% charge every day.
To resolve the problem, I bought a cheap charging port flex cable off ebay for about £4.00 which I thought was a bargin. After taking the phone apart (with help from a YouTube video) I replaced the port, turned the phone on and it charged perfectly. Then all of a sudden I lost all signal. I moved around the house, hoping to get the slightest bit of signal but no, nothing. I did a lot of research online as to why this has happened and everyone said it was to do with the antenna cable that runs along the left hand side of the phone so my immediate thought was to buy a new one. I did a factory reset to see if that helped but it did not. As I was desperate, the following day I went into town to see if I could find a shop that sold an antenna wire. I went in shop after shop but nowhere sold what I was looking for. I went into a shop and described my problem to the man behind the counter, and he knew exactly what was wrong. On the flex cable there is "REV" followed by a number, and he told me that if the replacement number is not the same as the original then the phone will have no service.
My original cable was "REV2.3" and my replacement cable was "REV2.2".
Long story short... when replacing the charging port make sure the replacement flex cable has the same REV number as the original otherwise you will have no service. Your problem is not related to the antenna wire.
I hope this helps!