That's what "friend" means.
The very definition of a friend is someone who knows you well, you know well, can be presumed to help you move**, and would never rip you off.
If you are not properly using the word "friend", stop! Language is the shared medium by which we communicate. It only works if we share meanings. If you say "friend", we have to take that at face value, based on the common meaning. (mind you: some nasty people manipulate/condition others to use words that don't fit. If someone asks you to use words like "friend", then scam alert.)
So, assuming it's legit...
They have no use whatsoever for your password or any of your details, and that's fishy. If they really want to pay your bill, all they need is a copy of your payment slip - you know, the tear-off section of the first page of your paper or PDF bill. That doesn't even have your account number on it. The most gracious interpretation is they are XY'ing: confusing the desired task with a particular way to do that task.
Social media sites don't help at all, using words like "friend" to mean nothing but the most tenuous connection. We also see people use the word "girlfriend" to describe someone they have only known by text message, and have never heard their voice, do not know their last name, and are actually being catfished for money. We see it everyday on travel.se.
A friend will help you move.
A real friend will help you move a body.
But the truest friend will help you move BOOKS.