How do i make my voice sound a lot deeper?

To make your voice sound deeper on the phone you should do things such as lay on your side when you talk (makes your voice instantly deeper) or not talk at all for about 30 minutes then try. As for a cell phone voice changer I know of none, but if you have a laptop at hand you can use a voice changer on that after hooking it to your phone. I don't recommend the laptop because it is very difficult to do.