It has been said sometimes that a Bitcoin transaction can be cancelled or reversed using for example double-spend.
Is it still possible? If Yes, how? If No, Why?
Especially when you sell services and goods and accept Bitcoin payment, you are worried about this.
So it should be a good idea to discuss this topic.
Once your bitcoin transaction has been send into blockchain explorer, it cannot be cancel anymore. But if you made a transaction in the exchange site platform without confirming it to your email or 2FA You can still cancel it as long as your not submitting a confirmation whether to your email or security code.