Debt Collectors asking for/providing contact details for a third party

[DonnysBrook]

A little while ago I was contacted by a debt collector looking for someone I used to live with. It's a complicated situation where someone else has run up a debt in her name, and I am in the middle of it. I tried to explain this to them and they said they would "investigate", which when I pressed them just seemed to mean they would keep trying to contact her. They asked me if I had an up to date address for the person they were looking for and I said "no" (because I don't).

I do however have her phone number. Are they allowed to ask for her details in this way and am I obliged/allowed to/prohibited from providing these?

[EnglandPi]

They have the right to ask anything they like and you have the right not to engage them in conversation and refuse to divulge anything whatsoever.

[atticus]

Of course they are allowed to ask. Whether to answer is a matter for you.