First off, the stereotype is not accurate. You can get a call center worker in the US who speaks with a foreign accent. In my neighborhood in a major US city, I hear foreign accents about as often as I do US accents. It also isn't true that accents correlate to how much authority a call center worker has. Level 1 call center workers all over the world are basically following a script and under very strict management.
Second, this is prejudice on the basis of national origin and race, which is bad. The problem with prejudice is that you are "pre-judging" --- making an assumption based on partial information. Sometimes that cognitive shortcut saves you time, but other times it doesn't. You should have to spend time on the call to determine whether the call center worker knows what they're talking about and has the authority to do what needs to be done. It really does differ from company to company. Accent should not be a cognitive shortcut.
Imagine if you said that employers discriminating on the basis of race was not because they are hating on that race for the sake of it -- they simply hate on people of a certain race because they have had bad experiences with people of that race before. That would be completely unacceptable.