I can't change my billing information or my credit card information - Please Contact itunes support to complete transaction

For a week now I've not been able to change my billing address or information OR change the credit card I wish to use on itunes. I've tried resetting the cache and warning messages, restarting my machine, and contacting itunes support. This is rediculous. I recieved an e-mail 4 days later saying that I couldn't use that credit card? The funny thing is, I have another account that can... So why can't I change it on this account? This is my main account and I want to use my main credit card. So finally they just deleted my old credit card information. This is fine, but I still can't add a credit card or even just change my billing information. This is absolutely ********. How hard is it to have your customers edit form information and store it in your database? Seriously, I'm so upset right now. Apple is known for being user friendly, how is this user friendly? I can't change my own billing information? I also feel like I'm one of the only people in my group of friends that actually pays for all of their music/movies, but now I can't even do that? This is so upsetting. Apple, I'm so disappointed in you. 😟