This article contains some setup-related issues in DSP.
Notes / Troubleshooting Guidelines
The user can see other other Advertiser which doesn't belong to them.
Check the user setup.
Normally user can see other company/advertiser because someone gives access to them by granting them a company level or campaign level access.
If yes, review previous ticket history.
Check on Zendesk for previous ticket request that could help explain why the said access was given to that particular user.
Review who is the requester of the ticket, is it the client or the CSM?
Proceed with revoking the access.
If you have discovered that indeed this was granted by mistake or by CSM/client request. Revoke the access to resolved the issue.
If there's no history when this was granted and who granted the said access, kindly flag this ticket for further investigation.