Just started the FNF and 5 minutes in, I tell Unicom that I’m taxiing to 28R. As I start taxiing I’m told by ground frequency - “where did they come from!?” - to contact them. I am then told to wait for clearance before taxiing.
5 mins in, and I’ve already been told off!
Are ground frequencies automatically connected to all the time when you join, or did this controller happen to join just as I start taxiing?