Hoteliers are being ripped off by phone scammers who trick staff into faxing information to premium-rate lines.
Con-artists call hotel receptionists asking for information about the property to be faxed to them, but the number - which always changes but always begins with the digits 070 - is bogus and connects to a premium-rate line.
The fax call remains connected until someone notices the problem and manually disconnects it.
So far, three Von Essen hotels - Congham Hall Country House in Norfolk, Homewood Park near Bath, and Bishopstrow House in Wiltshire - have been targeted as often as three times a day for the past fortnight.
Janine Black, general manager of Homeward Park, said: "It's very frustrating when you're trying to run a business and look after genuine people, and it wastes staff time."
Telecoms industry watchdog Ofcom said allegations of number misuse were looked into on a case-by-case basis.