I need to buy some mobile phones for a test system. I currently have phones that work at 900/1800/1900Mhz, and they work fine for Cingular and AT&T in the San Franciso Bay Area. We recently took them to Ohio, and they would not work for Dobson Communications (CellularOne). They use 850Mhz. My question is, if we buy some 850/1800/1900 or 850/1900 phones, they should work for Dobson, but will they work for Cingular? Yes, I will call Cincular also, but it takes a long time to get through to a technical person.