Foreign bank account

Hello,

I have an ameli account but I can't add my bank account information (RIB). I come from Slovakia and I have only Slovak bank account. I have tried three different times sending the relevant information (IBAN and BIC) by letter with no result. I have contacted your phone service, they told me Slovak bank is fine. What is the issue? My guess is that the problem is that Slovak IBAN has only 24 characters, compared to French IBAN with 27 characters. But the Slovak IBAN works no problem with other French services (CAF, taxes, mutuelle, salary...), I would like to use it for ameli too. What can I do?

Thank you in advance for answer.