Ok so I have $3.59 on my debit card so I want to buy an app that cost .99. It asks for my billing info and 3 digit security code and I enter in the SAME one I have used to buy 3 other apps before this this most recent time, it says invalid security code no matter how many times I try to close it out and try again! I even tried putting in my pin number just in case they meant that instead. I checked my address and debit card info and it has not changed since the last time I successfully bought an app. Some people say to change your payment method but I don't have one! plus, I don't see why all of a sudden they would stop taking my debit card when it worked before. Some people also say to change your settings somehow but where exactly IS the app store settings button??