don't be a stranger
US /doʊnt bi ə ˈstreɪn.dʒər/
UK /doʊnt bi ə ˈstreɪn.dʒər/

1.
used to tell someone you want them to stay in contact with you
:
•
It was great seeing you! Don't be a stranger.
•
We should catch up again soon, so don't be a stranger!