There are a few DTMF dialler chips to choose from

http://www.embeddedlinks.com/chipdir/abc/d.htm#dtmf

if you want to do it in hardware.plus a PIC. You'd need a
600:600 transformer too. Whichever dialler you select will
have an apps data sheet. The link gives the example of the
Philips PCD3311 and PCD3312. I've got a few TP5088s but
they're obsolete now. I've also used the Mostek MK5371 as
a dialler in a (gulp) tele-marketing machine, may my soul
rot in hell, but it wasn't my idea, honest

A parts search portal

http://ee.cleversoul.com/components.html

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Or you can generate the DTMF tones using the PIC

http://www.dattalo.com/technical/software/software.html

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