iTunes Store subscription payment

I’m not sure why but it’s not letting me fix any of my apps that are free and right now I have no money on my card and it’s asking me for my card but want to except it I don’t understand why it’s asking me for my card like if it’s trying to charge me because none of my subscription should i’m not sure why but it’s not letting me fix any of my apps that are free and right now I have no money on my card and it’s asking me for my card but want to except it I don’t understand why it’s asking me for my card like if it’s trying to charge me because none of my subscription shade have cost any money or be used I canceled the YouTube one when I lost my job awhile ago I’m just gettin on my feet working as a teacher assistant and I need to download a free app to use at work everyday and it won’t let me