Eviction notice

So our rent is due on the 10th of every month after that you have to pay a $20 late fee. We live in low income housing and told the office we would be 8 days late this month. We've been here almost 3 years and have only been late once by a half hour. She said that was perfectly fine to just pay the late fee. Well today I got a letter stating we have to pay the $379 AND vacate the apartment by 2/28/2020. It's Saturday so I'm freaking out because I can't call them. I know I won't know for sure without talking to them but does anyone know if it's just standard procedure especially after we had already told them and they were fine with it or what. I'm freaking out so bad. We have 2 kids and have no where else to go.