Dial 1471 afterwards, if it says "caller withheld their number" it is a UK caller who should obey TPS rules, if it says "we do not have the number" it will be an overseas caller who does not pay any attention to UK laws.
If it is an unwanted caller, say, politely, firmly and repeatedly "I am not interested in your services, please remove me from your calling list" Do not engage in other conversation. If they refuse to pay any attention to your request, say "hold on a moment" and put the phone down, and go and do something else for a while. Hang up the phone some time later.
I am TPS registered, and have Caller Display, I do not answer overseas call any more, I let them go to my answerphone. TPS has made UK cold-callers and canvassers dry up.
