Cell phone do not operate in the same frequency ranges that our radios do. I know that it may seem like your cell phone is the cause of your interference, but it's more than likely something else.
[link]http://www.spectrum.ieee.org/publicfeature/aug00/prad.html[/link]
Fields and frequency
Wireless communication systems operate at several frequencies in the electromagnetic spectrum. In the United States, cell phones operate in two main frequency ranges--the older systems near 850 MHz, and the newer personal communications services, or PCS, near 1900 MHz. European mobile phones use the Global System for Mobile Communications (GSM), a different technology than most U.S. phones, and operate at slightly different frequencies, near 900 MHz and 1800 MHz.
Over the years there have been a lot of things that have been tagged to cause interference with our radios, that never actually did. People get it set in their mind that these things are interfering and refuse to think otherwise even in the face of hard evidence to the contrary. Go figure.
Hope this helps.