Assuming she is using BT...
... she needs to report them to the nuisance calls department. Or perhaps you could, on her behalf, as she is so distressed etc ;-)

They will give her a month's free service of either anonymous call barring or 'choose to refuse'. Choose to Refuse is the one to try and get, it lets you bar the last incoming number- even if it is withheld, as the withheld part of the call is only from the exchange to your phone. Once she has them barred she can call BT and tell them it's in the barred list, they can then be traced and dealt with.

Word of warning: after the month they will charge for the service, so remember to cancel. Check bt.com for the prices, they're under 'calling features'.

If she's not with BT you'd need to check with the phone provider what service they offer.

If the caller is overseas there's little you can do about it I'm sorry.

Hope something was useful!
(randomstupidname would really like this signature field to be bigge, Mon 7 Sep 2009, 23:28, 1 reply)

Assistance
She's not on BT, but the current provider (NTL? Virgin?) may have something similar - we'll ring them up and ask :)
(calamarain just invented dehydrated water, Mon 7 Sep 2009, 23:39, closed)

Give em a rig
And see what they say.

Can you rig some form of recording device If so, then go menu and speak to the guy, get as much a poss then take it to the phone company and police. yes you have number ithheld but the phone company will have records. You may even be able to do a data protection act access and get the number. But by the sounds of thinsg you will probably need to invlove the police.

I have been drink so my advice may not be that sound. BUT judge by the person's tactics they will only respond to heavy fine and jail time.

StyX
(StyX is staring at you, yes YOU!!!, Tue 8 Sep 2009, 0:23, closed)

Sounds about right.
That crap can be traced with a court order, so she/you should be able to get him done with a little digging.
(Scritty Bakerman., Tue 8 Sep 2009, 0:55, closed)

"I have been drink"
Mind if I steal this expression? It's great!
( The Incredible Sulk Finally remembered his password on, Tue 8 Sep 2009, 1:38, closed)

Who's she with, if you don't mind me asking?
(Pope Jamiroquai III, Tue 8 Sep 2009, 1:11, closed)