Bad service

What a rude airline. I checked in online then got to the airport, queue was crazy and when I got to check in my luggage they said I can’t coz I’m ‘late’. Online it says check in closes 30 min before departure. I was there at 11:10am, when I was finalising with the check in lady at 11:20am, I was told I’m ‘late’ to check in my bag. Therefore I missed my flight because the agents weren’t willing to help. I’m not happy with this airline.