how to reset Nokia 3220 cell phone? Or how to replace the speaker?

I assume you haven't the user guide so go to www.nokia.com and service then downloads enter your phone model for the pdf user guide.

Guessing:
Meanwhile go into Settings on the phone and Tones see if you have set it on silent or you could do factory reset but that cancells all user settings to manufacture default which in theory should bring back the sound.

Bob
May 2012