Should I write a complain to Comcast for their business miscondu

I was charged a service by comcast that I never requested.
During the phone conversation, they told me, someone placed an order on behalf of me one month ago to upgrade my current service.
I argued with them and they finally removed the charge on my account.
But I'm very afraid it's a very dangerous thing for any Comcast customer.
So any Comcast employee who has access to our account can do whatever they want? Should there be a legal document that keeps the authorization from the customer?
They told me someone called in on behalf of me. So anybody can do that on behalf of me as long as he said he provided a door-to-door service and I agreed to upgrade the service? Should there be a signature from me even it's a door-to-door service? Do I have the right to get the person’s name from Comcast who called on behalf of me?
Should I just write a complain to Comcast asking them to do an investigation on this person? Since this kind of dishonest employee is very dangerous to Comcast?
Or I just forget it since they finally removed the charge on my account?
But the point is, I really hate this kind dishonest person and am really afraid that as a customer, we don't have any protection from this kind business misconduct.
Thanks for any advices!