Same problem here.
Mine has the exact same issues. My charge port stopped working, so I ordered a new port, installed it, and now I get 2G or nothing at all, usually with no bars or one bar. I even stood next to a known T-Mobile cell tower (As close as I could get), and it didn't help at all. I would really like to know what's up with the antenna replacement. It seems that this isn't just a coincidence, are the replacement parts faulty, or did we both install them wrong somehow?
I was very careful to install the new part exactly how it was before removing the faulty part. If anyone with more experience here knows anything, a reply would be greatly appreciated.