Fixing an issue around being unable to pay with a credit card is likely anything but a 30 min issue, unless there is some triviality happening, like a config issue. But even then you need to add tests for this. A day or two is the absolute minimum and that would be if this is just a config issue. If it's not, then think of weeks.
From the issue as described, the value "visa" worked, but "visadankort" didn't. Denmark's earlier, national debit card system is called DanKort. Nowadays, almost all DanKort cards are issued through Visa, so they are "Visa DanKort" -- within Denmark, there's the option to bypass some sort of fee for a lower cost of processing.
Presumably the value "visadankort" is there to distinguish these cards. However, they can be processed exactly as normal Visa cards.
This is not unique to Denmark, there are a list of card prefixes like this (see 4571 for DanKort[1]), but perhaps the different processing fees in unusual.
