How to let the ball traffic bypass the slow tunnel?

Question

network hardware

Greetings, there are several remote branches, each of which has a network on gigabit switches. All branches are connected by provider equipment to the CO, from which the Internet is distributed via DHCP.
Actually, all communication with the CO goes through a channel of 30Mb / s, but let's say if you raise the ball on a neighboring PC with a gigabit network, then the traffic still goes through a slow channel.
How is it possible to "with little bloodshed" make it so that the traffic inside the branch goes through its gigabit switches, and not through the provider's tunnel?