If you suffer from unwanted sales calls there are two key steps you can take. First make sure your number is ex-directory or unlisted. Call your phone service provider and ask them to remove your details from all listings. This is a useful step to prevent all types of unwanted calls, not just marketing related. Second step is to register with the Telephone Preference Service. The TPS is a UK organisation but other countries have similar organisations. The TPS operates an opt-out database that all companies making marketing calls must check their data against. Organisations with which you have an ongoing relationship are still allowed to call you provided they have sought your permission.