Expensive Parts failure in 4 years of ownership

I purchased Grand i10 magna in 2016. Drove arround 40000 kms. After 2-3 months I started hearing sound near driver door on rough roads. Hyundai service ignored my request to check. Some said it was suspension noise. They said it's not a issue. They waited 3 years so that my warranty gets over. Suddenly after warranty expired they started claiming that power stearing assembly needs to changed. I did not ask them to do anything except servicing but they detected this issue on their own. If it was under warranty it would get fixed free of cost. Now that costs arround 25000. This is Betrayal. Why didn't they detect issue earlier? They waited for warranty to get expire. I am really disappointed with Hyundai and never see it again in life.