can't change my billing info
I want to update my apps but every time I want to update my apps there would be a pop up saying there was a problem with your billing info and wants me to change my payment method but the problems is i can't change it. i happen after i subscribe 1 apps. i also can't make a payment. i have try so many times to change my billing paymnet and even looking for help but it's no use.. please help me, i don know what to do now.
iPhone 4S, iOS 9.3.5