How can I fix my heating?

I have a problem with main living areas heating staying on even when the time clock is switched off. It only affects zone one main living areas. Zone 2 controls bedrooms and is working fine. I thought it was a faulty timeclock which I have replaced but it is still happening. This is an intermittent fault and I sometimes have to turn heating on an off up to 10 times before the boiler actually turns off. Can anyone help please..........