boiler switching on and off itself?

hi, any help please?
i have a ferolli domina 80E with a salus thermostat. the boiler has just started to turn itself on although the thrmostat control should be off. i have tried resetting the thermostat controls but the boiler is still firing up. There is a light on the box as if boiler is getting signal from thermostat control box to turn on but the setting are low and weather warm so boiler should not be coming on.
i have had no problems until now. any advise would be appreciated before i have to call in the pros.
thanks