Selected the wrong listing agent when inputting a listing

The person who added the listing can modify the Listing Agent via Add/Edit,

type in the MLS #,

click on Residential, Commercial, or Vacant Land (etc.)

On the first page, click on Find an Agent. 

If you have issues changing the listing agent, you can send in a Status Change Form (from the MLS Portal go to Forms & Contracts and then MLS Specific Forms) addressing the change.