Company asking for bank details over the phone?

Few days back I was contacted by a company wanting to offer me some breakdown cover - they were cold calling me (as in I didnt request this first), anyway what they were offering seemed fair in service and price. So I said ok send me details and person on line said " we cant send you any paperwork as the government charge us for carbon waste etc" so he said what we need from you is your bank details we will then draw up the policy and then you can read it and nothing will be debited from your account until you go ahead with the policy and you can cancel. Now you are told constantly beware of fraudsters and never give bank details over the phone and whats this "cant send any paperwork out as will get charged by the goverment for carbon footprint" but they were more than happy to "send me paperwork" once I gave them my bank details. I said I would think about it and let them know. I have checked them out via the internet and cant see any other complaints about the company - but I dont know these people and feel if I give my bank details out would be same as if a stranger in the street stopped me and asked for my details. Whats others opinions on this.. Oh and said would call them Tuesday and they have already rang me 3 times today leaving messages, furthemore my phone number is registered with the ISP so unsure why Im getting these cold calls...