A BU has Access to all BUs corporate card activity

The client is facing the issue where all Business Units have the ability to view each other's Credit Card activity. A user with access to manage corporate cards and review corporate card transactions is able to view all transactions and all cards, despite only having data access for one business unit. There is a separate Corporate card program for this business unit. How can we restrict access to only those transactions/cards related to the business unit/corporate card program.

Could you please provide your inputs.

Thanks,

Mohan