How to professionally say “I am sorry, it won’t happen again” in English:

1.	I acknowledge the error and assure you that steps have been taken to prevent its recurrence.
2.	Please accept my sincere apologies, and rest assured, I will ensure this does not happen again.
3.	I take full responsibility for the mistake and will implement measures to avoid any similar occurrences.
4.	I apologize for the oversight and guarantee that I will learn from it to prevent any future occurrences.