As many have pointed out, if the seat has been reserved already it is the passenger or their agent who did it. Similarly, many have noted that some people don't like aisle or window seats. (No getting knocked by passengers walking to the lavatory, but still only 1 seat from the aisle.) As a customer I would be pretty cross with SQ if they phoned me up (or moved me without telling me) to accommodate someone who wanted extra space but was too cheap to pay for it. You gambled and lost, get over it.