Seat Selection Fee ; "Change" questions.
 

I have a few questions that I am having trouble finding answers for....
I actually ran into a problem with Delta once, when their online system tried to "double bill" me for a seat selection fee because I wanted to change seats to a seat that was the same price as one I already had paid for.

1) If I purchase an advance seat selection for $21, and then at a later time (before check-in) want to move to a different seat (also $21) will the online system recognise the fact that I have already paid for my seat originally and not try and charge me again?

2) If I purchase an advance seat selection for $21, and then at a later time (before check-in) want to move to an exit row seat ($42) will the online system recognise the fact that I have already paid $21 for my seat originally and only charge me the additional $21? (Not the full $42)

3) If I cancel my flight after paying for seat selection, will the fee be refunded?

From http://www.westjet.com/guest/en/trav...ion-faqs.shtml

Thank you. That is good to know, but I don't plan on cancelling.
I am very curious about the change questions. (1&2)
I assume this could be done over the telephone talking to a live agent, but I would like to know if anyone has any experience trying this online.
I much prefer not having to call.