It is not possible to change the frequency of the products, this will remain fixed at 433Mhz. 

With the older models however, in some ranges it was possible to change the code that the transmitter sends in order to avoid interference.

Please follow one of the links below that is of the same series type as your Byron kit for the solution to overcome this if interference occurs:

How do i identify my Byron chime type?

On the back of your chime unit, you will see a Byron Type identifier code at the top of the of the product information. This may be pressed into the plastic housing or on a label.

Here is an example:

Solution Links:

RX,TX and SX chime interference issues

SXi chime interference issues

DB chime interference issues

B chime interference issues

BY chime interference issues