Honda — Rust in RHS DOOR due to not proper water from drain holes at bottom of door.

I have honda city 2018 DL10CK6461 and also have extended warranty.
After 4years i am facing rust problem in my RHS DOOR bottom both corners from inside and outside due to not proper water flow out from drain holes present at the bottom both sides of door.
I contacted honda service centre and also wrote mail to honda company about my problem but they simply denied for any help but this is due to there manufacturing defect. They said me rust problem doesn’t come in extended warranty. I my really shock to see this type of response from such reputed company and also shock to see the quality of product they are using in car. I also have more brand car which are older then this car i have never faced rust problem in that. I have a good service record with company and always done my car service from honda service centre. Honda is not using good quality of products in manufacturing there vehicles due to which we as customer have to face these type of problem.