Question:

You don't specify why 11F was a more appealing seat than 4F. Was 11F in an exit row? Was that the reason for reseating, which seems the only possible reason I can think of for reseating, as one must be able to hear & understand commands given by F/A's in an emergency? Other than that, I can't even begin to think of why this would have happened.

An airline is required at all times to have a CRO on duty, so you could have asked for one right then and there, if you felt you were being discriminated against. At this point, I would write a letter to them, bringing in the ACAA, as mentioned above, and state that you wish this brought to a CRO for resolution. They MUST reply. And I would send a copy to the DOT, as well (make sure you show cc DOT at the bottom to get the airline's attention). That goes on their report card and they will handle it promptly.