Orange Broadband

tommy2k8

I switched from my £17.99 package to £12.00 package on Orange in February - the home starter. Apparently it included home phone as well. So, they changed it. However, since August I've been charged £26 a month. I live at home still, so my mum pays phone through BT and I pay bb through Orange, so really we don't the phone package.
Only just realising, I changed my package to bb retention at £14.99 (I said to myself I would change if they cbarged me more than the advertised £12 a month but then they said they'd charge me £150.
I asked them for a refund (as there is no point in me and my mum both paying for the same phone!), they said ring BT, who said ring Orange, who said ring BT, etc
One question:
Why did Orange start charging me £26 only from August and £12 Feb, Mar, Apr, May, June and July?