I've received a call from someone purporting to be from Virgin Media to check the security of my internet account. He said there had been unauthorised activity overnight on the connection. I believe this was going to be a scam asking for my details, so I said I don't do this over the phone but will check with Virgin media through their website.
How do I report this kind of scam (if it is a scam) to Virgin? How do I check to see if there really has been a compromise to my internet security?