ENDING A CALL: Turn off the power if it’s a cordless phone.
This has happened to me.The operator said they don’t quite know how it is done but it’s to with them being computer generated.The call remained on my line until I switched off the electricity where the base phone is connected.
On certain types of phone you can block unwanted calls.If you can’t understand how to do it ask someone to show you.It’s the best way although no doubt they can call from a different number.
How my heart sings 
When making s phone-call was expensive, we never had these problems. Now that it’s virtually free, the scammers have a field day and it’s had to keep up with all their tricks.
I find that an answering machine is very useful – just let all calls go to that but have it in earshot, so you can pick up the phone when you hear it is someone you want to talk to. You just need to tell your friends to hang on for a few moments, so that you can pick it up.
Thanks,MikeHe was very persistent..They told me recently the red button would do the trick.I have changed my message to the default one as well.
Yes, I have a very basic message that gives little away “Thank you for calling. Please leave your name and number and we’ll call back as soon as possible” So far, it seems to work.
I think that is sensible.I’d never realised it was because phone calls are cheaper now!