having dramas downloading app's

ussually wen i purchace an app it just ask's me for my apple id password then install's the app, now it say;s (please sign in required) then after clicking continue it goes to "payment method/payment type and all my bank details now... sugesting there's something wrong with the detail's in there, this step was never required before now and im unable to install app's now... can someone help me with this issue at all please?????

iPhone 5, iOS 7.0.6