I have almost the same issue with you, just I have been trying to contact customer support since January for three times. It's not being handled yet. To change a 1099k for the pas year, I understand it might be difficult since it's has already been reported to IRS. What I want to change is for the current year so by the end of the year they will have a correct 1099k. But even that I have been waiting for 8 months and nobody helps.
Yes, I have the same issue and no one helped me. I set up my store with personal tax information, and now I want to update the legal information in Shopify payment to LLC. I have been in contact with the shopify support team since July. It's 2 months now, and my ticket is still pending... I'm really disappointed about it.