AWS Billing Shows - Directory Service Charges

Since this pertains to charges, I would suggest contacting AWS Support, If you are unable to identify the source of the charges or if there's any suspicion of unauthorized usage, consider reaching out to AWS Support. They can assist in investigating and provide insights into the specific charges. AWS Support is in a good position to answer this question

Hope it clarifies and if does I would appreciate answer to be accepted so that community can benefit for clarity, thanks ;)

It could be associated to WorkMail, if you used WorkMail Services at any time this service creates Active Directory to handle users (depending on the configuration). Once you delete the WorkMail Service you have to delete the Active Directory too.

Same happened to me as well.