That's interesting, so it may be they are now checking the login profile of the person making the booking and the applicant details (they may have become suspicious if they saw several applicant appointments had been booked using a single login profile)? If not may be they tried contacting you on the number provided and weren't able to.
You should be aware that it is against the rules to sell PEO appointments which is stated clearly on the UKBA website (
http://www.ukba.homeoffice.gov.uk/about ... pointment/). See below for another instance which is different, but where an applicant had made two bookings and the UKBA had cancelled them because of this.
http://www.immigrationboards.com/viewtopic.php?t=123740
Who actually booked your original appointment? Did you pay for booking the appointment? Have you tried searching for and booking an appointment yourself? Solicitors or Approved OSIC registered Agents are allowed to book appointments for their clients.
See also:
http://www.immigrationboards.com/viewtopic.php?t=123046