Boiler not turning off

I have a Baxi powered flue boiler (not combo type) that is causing me some issues. It is not turning off when the controls tell it to, i.e. when the timer clicks off. I recently had the pump replaced as the previous one failed and since then the pump runs (from what i can see 24/7) and brings the boiler in even when the controls have it off. I have checked that the control radiator (in bathroom where boiler is located) is open and fully vented but i cannot understand why the boiler is running and burning gas when it isn't supposed to? I have tried everything i can think of.. bleed all radiators in the system.. turned the pump to setting 1 from 3 and turned the boiler down to low from 5. Help?!