What the other guy said. The main breaker shuts off everything downstream, but everything upstream of the main breaker in the panel is hot (ie the lugs). And they're pretty easy to hit. You'd have to pull the meter to fully deenergize the enclosure, and that's a pain in the ass to deal with. Generally, you need to call the utility, although you can always break that rule, but pulling meters isn't something I'd recommend to a DIYer because depending on the state of the meter base, there's serious risk of pulling a lug off and arcing it to the can.