The channel name is not the problem. The problem is that people will go to whatever channel they want and ignore any "official" support system. It's the same as the guy in sales who comes to your desk to bug you about something he promised a customer. He knows he's supposed to go through channels, but he's going to do what he wants, regardless of mechanism.

That can be solved with the right company culture and a good manager. If someone was disturbing my work in that manner I would mention it to my boss, who would probably tell me to not spend time answering them next time and direct them to the proper support channel. If it happened repeatedly, then my boss would escalate it with the salesperson’s boss.

They will keep doing it if they keep getting positive results. Eventually it's up to you and your team to set boundaries.

For sure, but then management gets unhappy because sales people are unhappy.

Alternatively, set up a #eng- or #dev- channel so you don't have to redirect anyone to #support-