margin call, page-9

geni,
I understand CFD's ok, however when I made my purchase I recieved the usual confirmation notice of the transaction which states
"Thank you for using IG Markets.

This message is to confirm that you have placed the following trade:

Date: x Jan 2009
Reference: xxxxxxx
Size: Buy xxxxx.0000 shares to open
Market: Babbcock and Brown CFD
Level: xx.00

To me this is a contract.I dont see how they can,retrospectively,40 days on say "hang on we are gunna jack our margin up 4-5 times."