Is there some way that i can go to my cell phone provider and have them make it so that my N810 can be my cell phone? Right now I have both a cell phone and my N810 and its really annoying to have to carry both.

The N810 does not have the hardware required to send or receive cellular signals. The N810 is not a phone. The only way you could make it a phone would be to open it up and somehow add the hardware (very complicated, if not impossible).

The only other way to make calls through it would be to use it as a VOIP phone, or a device that allows you to talk to other people over an internet connection. Google Voice + Gizmo/Skype makes for a good free VOIP phone. However, this method does not help if you have no wifi signal.

That is the exact same reason that many of us are excited about the N900. It's a mobile computer and a mobile.

a wifi dongle with the n810 might be an alternative. i've seen discussions of the"myfi" and others.

Why on earth would you need a "dongle"? The N810 has built in WiFi

He's referring to the MiFi 3G router as a dongle.

However, the OP said that he did not want to carry multiple items. If his/her provider is a GSM carrier, I would recommend moving to the N900 as an initial solution.

Beyond that, it would be a process of utilizing VoIP and SIP services on your N810 to duplicate some cellular features, however, you'd be limited by whatever wi-fi access points you are connected to. This would limit your ability to chat-in-transit, but in some stationary points be usable for use.