Sorry this happened. I'll ping @calyx our in house SL guru. Good Luck!
I would suggest you call/contact them and see if you can get someone a little higher on the proverbial food chain.
Explain the situation, and then ask that since you were misinformed about the requirements, but could still not afford to make payments that you would like to inquire about retroactive forebearance. It's just like it sounds - they retroactively apply a forebearance on those months so that you would not have had to make a payment (though interest would still accrue). They should send you a letter so you can get the CRAs to update correctly (Nelnet should inform them to remove the lates, but I wouldn't trust them to do it).
You could also try a goodwill letter campaign (search in this forum for samples, examples), but those don't always yield good results and might take a while.