actually in Korean the best thing you can do is say 아니에요, i watched a Korean video that explained that a lot of foreigners learn that 천만에요 is how to say your welcome, but in Korean spoken this actually is not natural and you shouldn't say this. there is no way you can emphasize your welcome because in Korean culture modesty is important so if someone says thank you you just reply that it's nothing, just like in vietamese when you say Không Có Chi, same in all asian languages

도와 주셔서 감사합니다, - 언제든지 불러만 주세요. maybe, you've ever heard above phrase in advertising text. or 도와 주셔서 감사합니다, - 뭐든 말씀만 하세요.