billing infromation

hi, my name is kemi. i have a iPhone 6 and recently I've been having issues with my phone. My phone won't take my debit card . It keeps saying my '' your payment method has been declined please enter a valid billing information''. Now I've never had this problem before, it just started to happen and because of it i can't update my apps on my phone. if you could find a solution to this problem and get back to me, that would be great. Thank you!