ripped me off good n proper

I purchased a settee on buy now pay 12 months which i thought was good at the time.This was ordered at the beginning of August 2013, however there was a problem with stock and delivery so it wasn't actually delivered until 27th September.
What did i receive at the beginning of August a statement saying the full amount was due and if the balance wasn't paid in full i would incur all the interest for the year that worked out at nearly £400.00
I thought hang on a minute the balance isn't due yet because it should be 12 months from September(end of) when i received the settee if anything should be November
I called to point this out to them and i must say they weren't bothered or apologetic at all. They were quick to point out to me that buy now 12 months is from date of order not when you receive the goods!!!! THAT'S NOT 12 MONTHS INTEREST FREE THEN IS IT MORE LIKE 10 MONTHS.They wouldn't agree with what i was saying...GOBSMACKED AND SKINT