I have a Samsung m610 and a N800 (running OS2008) with a basic Sprint PCS voice plan (through my work). I can connect my phone and N800 via bluetooth fine. But, when I try to use the phone as a modem, the n800 gives me a "connection failed to <phonename>. Try again?" message. My phone flashes a screen really fast, that as far as I can make out, states my username and or password may be incorrect.

I have tried both setting up the connection as data call and GPRS. Phone number is #777. I have tried leaving the username and password blank or leaving <PCS Vision Login> (literal) with no password. Nothing works.

Sprint has told me that they don't block internet/email access if you don't have a vision plan, though they do charge $.03 a KB if you don't.

So, what do I need to do in order to use my phone, as a modem for my n800?

Im pretty sure you cant tether a device under the pay-per-use for internet that and the M610 might have the port blocked ?? (2nd NAI)

pay-per-use would be the phone device only

blinjinx is correct. You would need the PAM plan to connect to internet via your phone's modem.