You'll need to have billing take a look at that. There isn't much any of us here can really do other than to suggest to enter it a few times repeatedly

.
Go to
http://secondlife.com/support/ (or just click the Support link at the top right here

) and if you're in the US you can simply call them (if you're not in the US you can call too, but then you'll obviously have to pay for the international call).
If you can't/don't want to call, click "Submit a ticket" on the support page, and under "Ticket Type" pick "Billing and L$" and just fill the rest of it out as well.
If you think your English might cause a problem, I would point that out, try to explain the problem as best as you can in English but also point out your native language. If someone on the support staff speaks it, they can help you in your preferred language

.
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If they aren't actually able to help:
* you could create a PayPal account, put your credit card on file there and then put the PayPal info on file with LL and hope it takes
* if you're not going to pay tier to LL/own mainland, you could buy your L$ from a trusted third-party exchange like SLX (
http://slexchange.com) but if you do that, please make sure you're buying from a trusted site (asking in the forums here is probably the easiest way to find out whether one is trusted or likely a fraud

). Of course this only a solution if you need L$, not if you want to own mainland.