Funny because an agent at the ticket counter at LGA was adamant to say that you cannot SDC from a nonstop flight to one with a connection (although you could do it the other way around). I politely explained that I have SDC'ed onto connecting flights numerous times. He wouldnt budged and insisted on charging the change fee. Went to the CRC and got everything taken care of within seconds. Amazing how there are some that have no clue what the rules are!