I have the same problem. Started a few days ago. Rings once at all times of day and night. Tried 1471 but number withheld. Phone rang 10 min ago and still no dialling tone back just all crackerly. Getting really angry with this now. Tried using mobile to call Virgin but 15 mins waiting time! It's very worrying, who is going this!!!
Welcome to the Community, I'm massively sorry to learn about the problems with your phone line.
I've been able to locate your account and take a good look at the line from our end for you, we're detecting some problems and I'd like to arrange for an engineer to come and take a closer look, if you're available.
I've sent you information regarding this in a private message, which you can view by clicking the purple envelope on the top right of this page.