I'm sorry to hear that. I lived in Jersey City and worked in Manhattan.
I had the 3GS and my $60/month iPhone transformed into a iPod touch in my apartment. Nobody could call me. And if they did it's, "Hi... beep, beep, beep". I got to know the smokers well since I had to go outside to get any consistent connection. Manhattan was fine... as long as you were outside. And at work it operated much like your phone.
I can't find the link I had, but there was a map that showed where the cell towers were and it also allowed users to report how the connection was in nyc. Maybe somebody here can post it.
If it were me, I'd go to AT&T and see what they can do- which is probably nothing except for threaten you with a termination fee if you are thinking about leaving.
Then I'd sell the phone on eBay, pay the termination fee, go back to a dumbphone and wait for the Verizon iPhone if you really want an iPhone. Or go with an Android phone. On Verizon. Unless you just got your phone, in which case I'd return ASAP.
I switched to a Droid for the service. The phone isn't exactly a looker, the app selection still sucks, the app store is still a mess, Android is laggy at times, the OS isn't as pretty as iOS, I paid that idiotic termination fee, etc.
But and this is a big, sexy booty butt... when you can make phone calls, receive them, and go onto the internet without an interruption in the service, it feels amazing. Seriously, the first week I was blown away that I could make a phone call and not say, "I'm in my apartment, the connection might..." beep, beep, beep (call failed on screen). I was getting calls from people and not the mystery voicemail 3 hours later! I was amazed that I could use the internet at home and get phone calls from my boss at work. It's magical. I don't regret switching one bit. And with the Verizon iPhone coming out soon, I can have the best of both worlds.