Why can i not pick up my local taxi company on my radio scanner? keynsham bristol?

Taxi companies have to pay for the frequency they use. Police, fire, and medical use the same type of radio frequencies, but these are available for the public to listen to on a scanner. In order to hear the taxi company, you would have to know the frequency that they use. Not all scanner's can search all frequencies and in order to do so, you would have to buy the right "crystal".