How awful! We had a similar situation where I work. A female employee who did anything and everything she wanted. We have customers coming back who are angry because she outright lied to them or misled them about things she did for them.
The branch manager took HER side over anyone who complained about her. In his eyed - she could do no wrong. Both are gone from the company now - they both retired - and we still have customers complaining!
She tried to corner me one day and I told her I wouldn't speak to her about anything that went on in the office without a manager present. We both ended up in the manager's office and she brought up something completely unrelated to work that she didn't like about me
I came unglued and told her and the manager both exactly what I thought about both of them.
After that, I did my job and they BOTH left me alone - I had enough on them to hang 'em both!
I was SO relieved when they retired!
We have one of those call in lines, too - and I told BOTH of them up front that I wouldn't hesitate to use it!
You did the right thing - customers have to come first!