Hi, @NewStart23 welcome to the community and thanks for posting, do you have the BT Sport monthly pass or is it a BT TV or Sky subscription? The reason I ask is that only the BT Sport monthly pass can be cancelled in MyBT.
If you have a BT Sport Subscription on BT TV or Sky you need to speak with the cancellations team on
0800 783 1401
Monday to Friday 8am - 9pm, Weekends and bank holidays 8am - 8pm