Hi! What do you mean “lock onto team chat”? As a developer, do you want to force your Players to use team channels only? Or as a user, do you want to write to team chat only?
If the former, you can set the ChatInputBarConfiguration.TargetTextChannel to the respectively team channel, like so:
local TextChatService = game:GetService("TextChatService")
TextChatService.ChatInputBarConfiguration.TargetTextChannel = yourTeamTextChannel
If the latter, you can prepend “%”, “/t” or “/team” at the start of your message.