Top tip.
If you're TPS registered but still getting telesales calls, ask the caller for the full details of their company, including Registered Office address and name of Managing Director. If they query this, tell them that they are contravening TPS guidelines and that you will report them with a view to getting their company either fined or shut down.
Did this to a cold call a while back and never had another problem.
Bear in mind that the person calling doesn't necessarily work for the company they are ringing on behalf of. Usually it's a telesales company who contract-out. So once you're off one database, it may remove you from all that the telesales company use.