You didn’t mention which country you are in.
In the United States there is Better World Club.
https://www.betterworldclub.net/bicycle-roadside-assistance
I have never tested it. Logically, they don’t have a specially trained set of bike mechanics standing by 24/7 across the country. Their page is pretty clear they don’t fix flat tires. Rather, it’s probably a tow truck service willing to pick up you and your bike.
Since you have a heavy bike, I would first priority puncture-resistant tires, possibly also with the self-healing goo inside.
For wheels that are pain to fully remove, there is the patch-in-place method where you expose the tube, find and patch the hole and and reseat the tire, all without removing the wheel.
With practice and preparedness, you can get a flat repair time down to 15 minutes, while practically every other option will cost more time.