Obsession with twngan

To my surprise, I just received a mail from Vanguard. It tells me how I could enroll my 401(k) plan, the retirement plan here in US. The weirdness comes from the fact that I have already enrolled my 401(k) with Charles Schwab, the provider of my company. Vanguard is actually the provider for Amazon, and somehow they thinks I'm still working here, even though I finished my internship 17 months ago and I declined their full-time job offer some 15 months ago, and I have never participated in their 401(k) during my internship.

What I don't understand, though, is how come their payroll department does not make the same mistake and keeps paying me...