Demon's Late Invoicing

I've just been overwhelmed by Demon's invoicing - they've just sent me
an invoice to renew my annual b.b. subscription which expired THREE
months ago. They did not invoice me before August to warn me to renew.
No - they waited until I was well into the new contract year. They
KNEW that I wanted to cancel my Demon b.b sub. because I want to
switch over to the Post Office for broadband and landline. Demon will
not allow me to switch to the PO and I'm pissed off with BT's
outrageous charges. So both BT and Demon lose my custom. But nw Demon
are refusing to let me have the MAC code to switch to the PO until
I've renew my subscription to next Aug (2009). This effectively forces
me to stay with BT until then too. CJB.