If you are still within your Fixed Term Contract for Halo you can not "downgrade" to another package with out incurring penalty fees which is more or less the amount of money you would pay until the end of your contract.
If you are out of contract you can downgrade but you will need to call BT 0330.1234.150 and you may find that the BT staff are less than helpful in "allowing" you to downgrade.
You need to be insistant and tell them that you are prepared to move to another provider if BT can not/will not facilitate your request to downgrade.
