Manager forced me to give my boss's number because he claimed I was being "disrespectful" toward customers. Since when does "I don't work here" become disrespectful you POS? Seriously next manager to call me out on that's going to get a lawsuit.
I think I know the situation you are in. I was in a situation like that once (different, though) and asked for the CEO office number. Not saying you should, but the comment reminds me of my own situation. Bad bosses are idiots (and managers don't manage anything, they pass on orders, that's it)