I had the same issue. Got accepted a year or so ago having submitted my original form. When I asked about DD from my UK account they said no bother just send in another form with only the DD bit filled in (didn't want to fill in DD on the original form if it was going to be class 3!) so I did so. Earlier this year they got in touch by letter to say I never provided my details around employment etc - they had put up the second dummy form (used for DD only) and so the system said class 3 again.I understood that, which is why I provided my UK bank account details on my original form. I still have my UK current account, and I also have a Wise account with a UK IBAN.
Had a whole load of hassle but got back to class 2 and was told I'd need to again submit a DD form for yearly payments - I just said I'd make a manual payment and it would mean having to ring them every year to check the class 2 payment for the tax year I'm paying.