Does LingQ accept any other credit card besides from Visa or Mastercard?
For instance, Brazilian elo credit cards?
Give it a try, if your card supports international online payments, you should be able to upgrade with it.
It looks like you should be able to use your elo card through a PayPal account https://www.paypal.com/br/smarthelp/article/quais-cartões-podem-ser-cadastrados-no-paypal-faq1833. Have tried setting up a PayPal account using your elo card and then using Paypal to pay for LingQ?