Welcome ,I will give a full and clear answer to your question, please make sure to reply to any questions I have. They may be essential to my reply.
Hi theres a good chance your Card or address details need updating or other problems in the account such as clicking an agreement need to be updated .
Your billing info may need to be updated , using your PC web browser.1. Go to http://myinfo.apple.com2. Log In with your Apple ID3. Update your account info. Check each section and for agreement Accepts etc that may be presented . 4. Check the Address book and Phone numbers - Please match that info with your credit card.5. Once completed save and log out , then open iTunes and update the same billing information to the letter . See Store Menu , View my Apple ID . If this does not work then the problem is an internal issue , and not Software related or info related. Moving house or a change of address can cause similar issues , It possible the change in Phone account has created an issue , but again this will have to discussed with Apple Directly as they have access to your details .You can email or phone apple support for help , they may be able to give you clues to why your Apple ID setup is failing , or your password XXXXX help you set up an account successfully or reset your current one ..http://www.apple.com/contact/There are many locations and contact numbers on the contact page above , please find the area phone number nearest to you or use email contact .There is also a remote possibility that you have an outstanding payment that needs to be cleared , again please contact Apple as above and explain your issue and check your account is up to date and paid up to date with no outstanding charges due..I hope this helps , please remember to press accept on the green button .Thanks .
Also make sure to update itunes to the latest version .
Apple menu software update . Or use the app store .
If using PC , go to Start menu , apple software update .
Or Apple.com/itunes , make sure to use itunes 64bit if using windows 64bit .