Vauxhall Zafira both radio and information switches on the steering wheel are not working.

i have just recently purchased this car, the radio as been changed to a JCV radio & CD player before I purchased the car. The drivers manuals came with the car after reading them i tried to change the settings on the radio using the thumb wheel and switches ( nothing happens have to use the radio controls for volume and changing channels.) I then tried to too go through the information screen computer to check miles per gallon etc once again nothing happens. I do have date, time and temp showing constantly but am unable to access any other info,