Set restriction for sending master data to GTS

I need your assistance.

Customer use ECC6.0 with multiple branches all over the north and south America. Each branch is divided by company code.

Management decided to exclude South America branch’s  master data (customer, material and vendor) to be transferred to GTS system.

How to set restriction by company code, or sales org to send master data to GTS system???

We tried to set restriction from user exit but it did not work.

We also tried to set it from BD64 but it did not work.

Please advise if any of you have ideas how to set restriction to send master data to GTS?

Thank you in advance!!