Hi my name is Chris and I have had the exact same problem twice now having to do with billing and a distinctive absence of an option that may in fact help out some other users that may be going through the same problem I have experienced before.
My problem is I add funds to my wallet with a credit/debit card. Just like forgetting where your keys are or over time you get new credit cards. These have new numbers that for them to be used on PSN have to be changed. This is the second time that i have had to go through a LONG procedure including talking to a live technical support technician. In the end the only real suggestion they can come up with is to purchase a card with a code for it. It seems that your system doesnt like for whatever reason changing your credit card. It usually takes me days to resolve this issue without buying a code based card. My suggestion to perhaps alleviate this is to add a couple of options to the account and billing sections when you log in on a computer. The first being to add a new credit card. The second being to be able to choose which credit card to add funds to your wallet from. The third and final suggestion would be to be able to remove the old and no longer active credit card. I believe this may help alleviate the problem i keep running into. In comparison it is pretty sad that i can apply for a brand new credit card. recieve approval for it and go shopping online with it before your system even registers a credit card i already have and have used in multiple countries.
Just my two cents from a concernedand slightly annoyed customer.
I don't know what the issue is with your credit card use, but it isn't a very common experience based on other posts to this forum. As for managing PSN credit card information from a PC, Sony already supports that. You can fund your wallet, and change billing information, from the Sony Entertainment Network web site www.sonyentertainmentnetwork.com via the "Manage Account" link on the home page. It doesn't really let you do anything that you can't do on a PS3, but it does provide a different user interface. There should be anything difficult about deleting one credit card, and adding a new one. At least not for most PSN users. PSN only supports one set of billing information at a time. It's not Paypal.