The name of this caller seemed to be Vanguard, but that was over a year ago in 2018, so it could've changed by now. This is a toll-free number.

Vanguard is an investment management business. It was started in 1975 by John Bogle, and had over $8 trillion assets under management in 2022. They offer mutual funds, ETFs, brokerage, and advisory services, that aim to be low-cost.