I sent a begging email to synchrony asking them to take my payment and reverse the interest.
They’ll probably say that unfortunately there is nothing they can do cause it’s run by robots and I’m an idiot.

Why did I just do the equivalent of setting almost 2700 dollars on fire?

I didn’t even know it was a deferred interest account! My husband signed up for it to get our son braces and didn’t even clear it with me. And I’ve been doing the remembering to pay it and dealing with the account ever since.