If you are chatting, you can say "下次再聊吧"., suggesting you want to call it a end.
If you are intended to refuse a thing, you can say "改天再说吧" or "下次再谈这个问题吧"., suggesting 'No'.
Humility and compromise are ideal in Chinese daily life, even today. It is usually unwise to refuse others diretly like 'American way' in China.