A way to simply have someone phone my computer so they're on a cell and I'm on my mic

I don't know if this is a newbish question or not, but does anyone know of a way to simply have someone phone my computer such that they're on a cell and I'm on my mic? It seems like such a simple thing for this day and age, but my attempt at a Google search is resulting in things that aren't exactly what I mean, such as where I can phone them first, but would have to incur charges, as if I'm using a cell myself instead of a mic. Does anyone know of a way, a site, or a software, to make such a setup work? To be clear, someone using a cell phone--not a mic and not a computer--would somehow "phone" my computer/a software I have, and I would hear them through the speakers as usual and communicate by my PC mic--not a phone and not a cell. It doesn't make a difference to me who phones who first, so long as I don't incur charges by phoning them first--otherwise I'm only interested in having them -phone- my -computer- first.

I am lost does your computer have a phone number? Mine can do what you talk about but it is through my cell phone and to the computer over blue tooth.

Only thing I can think of is Skype, but you have to pay for calls to anything other than another Skype account. My parents stumbled across something like that a long time ago, but I don't remember what it was called, as it was at least 10 years ago.

Skype and Google Voice.

skype ! but i think the person needs sykpe on there phone.

Google voice can call a phone for US and Canada for free.. but you have to do it the other way, meaning the PC will call the phone.