Issues paying Vietnam visa application fee, cannot contact support, please help

Application service says it accepts Visa cards, but when I enter mine, it doesn't accept it. I called my credit card company and confirmed that the transaction is not getting declined, nor did their system reject it as suspicious; the transaction is never even attempted.

Stuff I've tried:

• Contacting them through the support form: Waited over a week, no response.
• Contacting them via the provided email (foreigners@xuatnhapcanh.gov.vn): Delivery failed after 48 hours.
• Calling the payment processor via the provided hotline at (+84)368736616: Rings a few times, then immediately drops.
• Calling the immigration department hotline at (+84)02438264026: Error saying the call couldn't be completed.

EDIT: Resolved. A very generous comrade has trusted me enough to let me use their bank card to pay the fee. Thanks to those who responded!