외국인 택스 리펀 Tax refund in Korea VAT refund Korea korea entry requirements 공항 환급 방법 korea travel tips Myeongdong tax kiosk missed last subway Korea 한국 세금 환급 tourist exit procedures Korea tourist medical emergency Korea esim korea korea mobile internet overstay exit risk Korea korea sim card visa free korea immigration overstay decision Korea korea tourism guide travel to korea tourist overstay Korea consequences k-eta korea Korea tax refund korea connectivity 서울 쇼핑 환급 hospital visit tourist Korea late night bus Korea night transportation Korea taxi at night Korea