OK, I decided to try again since my Viber credit wasn't going down despite 10 minutes being on hold.
So after 70 minutes on hold or so, someone picked up but he had a bad accent and the call quality was horrible.
He told me 5K and 7A were the only throne seats available.
So I asked him to assign me 5K and then he put me on hold for another 10 minutes and he came back and said he couldn't make the change, said he should be able to but couldn't.
So I thanked him for trying and gave up.
Something was off with this booking, as I couldn't access it on swiss.com and he evidently couldn't pull it up with the LX confirmation number nor the ticket number.