Signing up for Asahi Net credit card hurdles

I recently tried signing up for Asahi Net for our new rental in Tokyo and ran into some issues with entering my credit card. I have a debit card with a local bank, and also an international credit card, both of which should have been accepted according to their website. Each time I entered it I always got the same response along the lines of the name I entered doesn't match the name on the contract. I did all the things you'd expect and more (order of names, english, katakana, half width, full width, etc.) but nothing worked.

After researching a little I came across this post from 10~ months ago where someone else had the exact same problem that I had and found a work around by calling, but there was no resolution for why it didn't work. https://www.reddit.com/r/japanlife/comments/17ahoti/asahinet_acceptable_credit_cards/

I decided not to sign up for that plan for a variety of reasons (still trying to figure out the right one though!) but I did also enquire with Asahi Net to try to understand why I was unable to enter my credit card details. I got a different response to the other person, so posting it here in case it helps anyone else trying to setup internet in the future.

My question:

Hello,

I am trying to apply for FTTH with FLET'S howeer whenever I enter step 5 and enter my credit card information, 
I receive the error "* The name on the credit card must match the name of the subscriber."

I have checked and the name is the same. I have tried in English and Japanese (Katakana), including full width and 
half width and different name ordering but it always presents the same error.

How do I proceed?

Their answer (shortened), with the interesting part highlighted in bold:

* There are various reasons for not being accepted by the credit card company, but regardless of the reason, the customer would always see the message of "invalid entry",
“The name on the credit card must match the name of the subscriber.”,  from 
the perspective of individual privacy security.
* Please also contact the credit card company, as they might rejecting our request
 due to the card limitation or their preference.

So, the incorrect error message is a feature not a bug, and you should somehow guess by yourself why their system won't process your card when every other website will.

If you take anything from this post, it's this: don't waste your time trying different variations of your name — it's like not the issue.