Re: estimated net "benefit" of £5.7bn by 2020
You can certainly phone up and demand a refund, you can even request a reduction in your payments. But whether you get them or not is another matter. If you can get someone at the company who actually gives a damn or is getting hassled about the number of calls they are not taking, or the time the calls they are on, and they can give you the time to try and sort your account out, you'll be extremely lucky.
Next, the requested reduction, if the CSR does put the change into the system, the system will analyse it, if it meets the requirements (and it won't) your monthly charges will be reduced, what normally happens is that the system will increase your monthly charge and you will have to phone in again (don't bother writing or threatening to leave (the letters will be put at the bottom of a pile for another CSR to deal with) while the company is attracting plenty of other suckers in with "great" deals.)
The voice of experience at both ends.....
Biting the hand that feeds IT
