How to stop Cust. master data update from CRM to ECC

Hi all,

We have the following 2 scenarios running:

1. Creating Prospects in CRM --> replicates to ECC

2. Creating Customers (Sold-to) in ECC --> replicates to CRM

Now we have found that changes in Customer Master in CRM are also updated in ECC which should not happen, please suggest a way to stop this and also not effect Prospect replication (CRM--> ECC)

BR.