azazyel:
Two options - turn the phone off (nobody reaches you, hehe). Or screen your calls with Caller ID
I have a $30/month plan with Cingular. 250 anytime, unlimited between 9pm-7am and on weekends. Works for me, although I come close to the anytime limit each month (more so when I'm not in school, hehe). Cingular is TDMA here, I have the Nokia 3360 (got it for $25 when they were running the 1/2 off sale), and it works just fine. From what I've heard, this is the phone to have now.
I've had the phone for a month tomorrow, and I've used it for 8 hours..I don't have the problems that people on Cingular in CA claim to have. Nokia is coming out with two new phones within the next coupla months. For GSM (Cingular on the West Coast, and in the Southeast, Voicestream, a lil part of AT&T) Nokia is releasing the 8390. For TDMA (Cingular in the midwest, AT&T most places) they are coming out with the 6360. I don't know of any new CDMA (Verizon/Sprint PCS) Nokia phones - Sprint already has a bunch of cool phones (from 4 of my friends that have it, the service is fine, but from others I've heard more complaints than any other carrier) and they don't carry any new Nokia's.
wirelessadvisor.com (industry reps) and howardchui.com (more end user, hacker types) have good information, I frequent forums on both sites.