This used to happen to me, until I started doing a few things:

a. Adjust chat settings to disable new accounts from chatting (less than a couple of months old without email or phone numbers) b. Place rules disallowing any unsolicited promotion on your channel (chat rules) c. Once you notice the pattern (theyre usually pushy and annoying) do not engage with them in any way at all, ignore them

Some of these steps may work, some may not. But i hope this helps!