Most cell phones are in the 800MHz band, and above. However, most if not all today are digital, and can not be monitored with scanner radios, even if the scanner radio is digital.
Cordless phones are at 900 MHZ, 1.9 GHz, 2.4 GHz, and 5.2 GHz
Cell phones are 850 MHz and 1.9 GHz in the US and 900 MHz and 1.8 GHz in Europe, and any combination of there other places around the world.