Yes you get flight credit(s) regardless of what method you use to purchase tickets on Southwest. If you purchase with the Southwest VISA, you will get "reward dollars" on your Chase statement which eventually will turn into additional credits every time you reach $1200 worth of spending. For every dollar you spend on the SW Visa card with Southwest or their travel partners (Marriott, Hilton, Avis, Hertz, etc.) you get double "reward dollars" (basically 1 credit for every $600 you spend with Southwest or its partners, 1 credit for every $1200 you spend on anything else).