It's not just a problem suffered by PlusNet customers I know.
Does everybody check their monthly phone accounts? If not then they should.
I look at mine probably once a week and I just came across a call that has been charged to me that I imagine was made by an engineer while testing. A 1 minute call to 123 , are there still people around who use the telephone to find out what the time is??? I'm surrounded by devices that are correct to the second because they regularly update themselves automatically and without any charge.