Q: when i enter my security code for my credit card it says its invalid

It seems that the store will report the security code invalid if there are any errors.  I kept getting the security code message with the correct code, but I had made a one digit error in my card number.  Recheck everything.  This error will also be generated if the address is not exactly the same as the billing address the bank uses.  Be sure you include St or Ave, N or S, etc.

Long thread on security code error with some things that worked for some people - https://discussions.apple.com/thread/2045791

everytime i enter my password in for my itues to update my apps its saying bank card declined please can you help me

had this same problem you can try this Go in to itunes and sign in to your account after go to purchase history if you have unpaid apps then thats your problem the best way to pay for them is to buy a gift card and pay for them that way. because your credit card dont what to work. i download a app that bypasses the app store security so when i pay for a app it just downloads it with out hafting to view the billing information but it added up and thats what i did to fix it.