This is just a thought, but no-one has mentioned broadband yet .. Do you have BT Broadband on that line? Would that be billed on the same bill as your BT Phone? I'm not a BT customer so I'm not sure how their billing works.. but if "BTB" is BT Broadband then it makes more sense to have line rental and then a broadband charge... It would also mean that you are getting your line rental free as the £34.80 is being refunded and you are paying £25.50 a month for your broadband. Does that sound reasonable?