AT&T gave me a messed up connection?

A storm completely blew out our internet access and cable for three days. Once AT&T finally sent out a van to help us, the employee was very quick in giving us a new 2WIRE SSID and password. When I enabled wi-fi access on my iPhone 4, however, it completely shuts out once i leave the room where the modem is located and switches to 3G. This is also happening with my sister's laptop, it appears you have to be in extremely close proximity to the computer to get wi-fi access. Any way to fix this?!

Unfortunately you more than likely received a defective gateway out of the box.

It's highly probable that you won't be able to do anything yourself to fix it. You need to have ATT either send someone back out to replace it or have them mail you one.