i ordered bt line on wednesday and it went live on friday . i now dont need the line and will be charged £70 to disconnect i have no account number . i was wondering if they can do this or do i have a cooling off period before they charge me?

Why should BT or anyone else let you have all the setup costs for nothing

The line has been provided, you must pay if you no loner need it. It's not BT's fault, they've had to pay Open Reach for the work.