Thanks, that's very clear. And what about:
Today they offered me a £10.75 discount for a 12 month period as of today, then changed it to £8.25.
Is that per month? Starting when? Backdated or from when you agree? And will they remember it
The £10.75 pm discount for next 12m looks the correct figure to repay you for the overpayments in Sept to Jan:
Overpayments in Sept to Jan = £2.80 + 4 x £7.75 = £33.80
Extra discount over next 12m = 12 x (£10.75 - £7.75) = £36.00
but not the £8.25 pm discount which would leave you out of pocket by £27.80
Do you know when the line rental went up by 55p? The increase in Sept looks almost like 5 of these rental increases.
Frankly if you have a transcript of them agreeing a £7.75 pm discount for 12m, then you shouldn't have to keep phoning up every 3m and anyway they didn't even do it fully for the 1st 3m.
1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 20 Meg WBC