The MLS rules prohibit seller contact information from being displayed on the Public MLS websites. Your contact information and showing instructions will be available to all Realtor members of the MLS.
The information below is what is exported from the RMLS to all of the various Public websites i.e. REALTOR.com, ReMax.com, Hasson.com, PortlandMLSDirect.com etc. As you can see, there is no contact information for the Seller or the Listing Agent.
When a real estate broker performs a search on the MLS they receive a report like the one below. It has all of the information about the property, both the public and private fields. The Sellers contact information, commission being offered and showing instructions are available to all agents.