Using IAM Identity Centre with Monitron and ASC

We are a distribution partner with a reseller in a dedicated payer (so they retain Organization features and can use SSO, amongst other things). They have enabled IAM ID Centre at the organisation level and have added multiple users (from all different end user companies). These users are using Monitron but when they begin to type their user name in, a list of the complete SSO directory is presented to them. Not good because they are all different end user companies. How do we isolate the users from each other so they don't see this list?