I assume that there was no promotion (mo money, supervisory position) associated with this change.
I can see how this could be equated to age discrimination, first because you were replaced by much younger personnel, you don't have any experience in your new role, the employer's rationale about you being more respected is extremely weak (no one knows who they're talking to on the phone, and there's no statistical evidence that an older customer service rep gets more done in less time.
All of which adds up to your being transferred as a pretext for "managing you out" of the organization, due to your failing to perform, when in fact, the reason is that the employer doesn't want an older worker who is more risky for all sorts of reasons (health care, salary, etc.).
The weak part in your case is that there doesn't seem to be any overt "adverse employment action." Age discrimination requires that you suffer some injury (less pay, worse schedule, demotion from management, bad performance review, etc.). It's not clear to me that you are really suffering a substantial injury as a consequence of the transfer.
You might want to consider asking your supervisor to return you to your former job and tell him/her that you feel as though this entire move has been designed to encourage you to quit, and see how management reacts to your suggestion.
Maybe they will rethink their position -- or, maybe they will do something stupid that will make your case more clear.
Usually, I think it's a waste of time to talk to HR, because they're in business to help the employer -- not the empoloyee. But, in this case, with things sort of vague, shaking the tree may actually be a way to shake something loose -- or, maybe even resolve the problem.
Hope this helps.
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