Check this out from a forum post I found at [Reddit - Dive into anything]:
I've successfully used the HT9032C chip (see: http://www.holtek.com/pdf/comm/9032v141.pdf
). It connects via UART pins (D0, D1) to the Arduino.
I can confirm it works in Canada but should work in USA too. I've read that many telcos in Europe use DTMF tones instead.