payment issues

so basically, i recently removed a visa gift card from my payment options, which was my default and only payment option. now, whenever i try to download anything, even if it’s free, it asks me for my payment option. before i was using the visa gift card, i had been purchasing things with itunes gift card and never had a credit card entered. i’ve never had this problem until i had removed the visa gift card and i can’t download anything at all. i don’t know how to set it to use itunes credit again.