A/C knob does not turn the A/C off



I bought a Honda Civic 2002 4-5 weeks back. Its A/C is always on. When I push on the A/C knob it does not turn the A/C off, and the light in the knob remains on, and of course A/C remains on as well. I can turn the A/C off after trying several times for few days. However, if I turn the fan on or press another knob, the A/C comes back on again (the A/C knob has its light on) even though the A/C knob has not been touched. Can anyone help me with figuring out where the problem could be and how it can be resolved?