Loan defaulted even thought I was paying?

My loan defaulted and my whole tax return was credited towards it. Now they are giving me two options, consolidation or rehabilitation. I haven’t looked at consolidation yet but the other option was a monthly payment of $700 unless I can prove bills for smaller??? They confirmed that I have made on time payments for the last two years but that I had not setup a payment plan so it doesn’t count as on time? Also, these loans have existed since 2013, why default now? All of this stems from loans made through Everest university, a college closed due to fraud. I’m pretty sure I set these payments up based on their communication. Who do I reach out to regarding the payments but no payment plan?