You can force gateway to be considered down and removed temporarily from load balanced internet connection. You do not have to make any other changes to the firewall. This feature is inbuilt directly into pfSense itself.
Mark Gateway as down in pfSense
First, login to your admin interface.
Next visit System > Routing
Click on Edit gateway icon for “A_4G_WAN” (4G LTE gateway which is running out of bandwidth) > scroll down and select “Mark Gateway as Down” option:
Click on the “Save” button > Apply changes.
That is all. Now your 4G internet connection disabled, and your firewall should work in failover mode over other internet connection. To verify new settings click on Status > Gateways:
You can reverse force state gateway anytime and bring back the internet interface into production again by visiting System > Routing > Edit Gateways button > Remove “Mark Gateway as Down” option > Save > Apply changes.
I hope this simple technique may help someone to save money or some other purposes as per your local requirements without removing load-balanced links.