Comment by warp
You physically go to the bank.
The electricity company has their own employees to deliver paper monthly statements to all their customers, they can attach other communications if needed.
My bank has a connection to the electricity company, and can look up in realtime what my open balance is, which you can view and pay in the banking app. You can also pay it in cash at various offices (e.g. Western Union) around the city.
You can also just give the electricity company permission to automatically take it out of your account every month (ppl don't trust the electricity company to get the amount correct, so folks don't usually do this. I do this for the water bill though).
(this is my experience living in Ecuador for 10 years, I'm from the Netherlands, most of this is weird to me :)
Three weeks ago I was part of a comment thread on this very site, where people were wondering why banks still had buildings for people to go in to.