Keep in touch.
Good-bye. (Sometimes a sarcastic way of saying good-bye to someone one doesn't care about.) Nice talking to you. Keep in touch. Sorry, we can't use you anymore. Keep in touch.
keep in touch
(with someone) Go to in touch (with someone).
keep in touch (with someone or something)
and remain in touch (with someone or something); stay in touch (with someone or something)to maintain communications with someone; to maintain up-to-date knowledge about someone or something. After my neighbor moved, we still remained in touch. I want to stay in touch with my office over the someone or something, in any combination weekend.