Cell Phone Service Providers CSRs

My son’s Sidekick III just lost its backlight and started showing corrupt displays. I called T-Mobile to do a warranty exchange and got the usual CSR: Someone who is barely understandable, is over-familiar (which is annoying not because I want to be called “Mr. Gibbs” but rather because they use you first name so much it is simply irritating), and downright smarmy. Can anyone explain why the cell phone service providers train their staff to be so pathetically ingratiating yet ignore the fact that most them have horrible verbal skills?