Here are some particularly useful links regarding Bitdefender order and subscription management:
https://www.bitdefender.com/consumer/support/answer/29455/
https://www.bitdefender.com/consumer/support/answer/29362/
https://www.bitdefender.com/consumer/support/answer/29251/
https://www.bitdefender.com/consumer/support/answer/29081/
Should you have questions, feel free to drop them in the comments below.