How to stop spam
Spam has become a modern plague. It is important to know how to minimise the problem.
For spam calls, sign up your home phone and mobile to the Telephone Preference Service http://www.tpsonline.org.uk. It is illegal for UK firms to call those who have registered. There is also http://www.silentgard.com/register.aspx which helps minimise the number of silent calls you get.
Sadly, if the calls originate from outside the EU there is little that can be done. If it happens, be firm but polite, tell them you want to be taken off their list, will never never buy anything from them or any company associated with them.
If we all deny them business, it cuts their return on investment and should reduce the number of calls they make.