We have a charge on our credit card we don't know what account it is for.

Hi Julia,

Since you mentioned that the subscription is managed through a third party, I would first recommend contacting them and asking whether there are any Microsoft subscriptions associated with your business account that could be generating this charge.

If they manage the account, they may be able to identify the subscription directly. If they cannot determine where the charge is coming from, you can ask whether they are able to open a support ticket with Microsoft on your behalf. Microsoft Support may be able to investigate the billing transaction and determine which Microsoft subscription or tenant the charge is associated with.

For Microsoft 365 business subscriptions, access to billing and support options is typically limited to users with the appropriate administrator roles. If you are not an administrator, you may need to work with your third-party provider or your organization's IT administrator to contact Microsoft Support.

I hope this helps point you in the right direction.