Debian 10 auto upgraded to Kali rolling

[Saurabh Kannaujia]

Hello,
I was using debian 10 and enjoying it, once I run 'apt upgrade' and it
changed to Kali linux rolling. I don't know why this happend but I want to
comeback to Debian. Is there any way to comeback or do I have to reinstall
again(ugh!).
Help me out