Those gazillions of "service" agencies making calls and sending brochures are just agents for private carriers of Medicare supplement and Medicare Advantage insurance plans. The callers and insurors have no relation to Medicare, and are not federal employees or contracted out folks As most folks don't have a clue about all the options available to them (here in little ol' Connecticut there are over 100 Medicare Advantage and Medicare supplement policies offered by private insurers).
The $1700 "savings" - that's the yearly premium for Medicare Part B (doctor and treatments); it's usually deducted from your monthly social security checks. The private supplements and Advantage plans usually cover the $1700 premium, so you in effect get an extra $1700 in your Social Security checks each year.
I was a Claims Rep (CR) for Soc Security for about five years. The private plans are now so complex no one - really - no one can figure them out. You make a guess, choose a private plan if you want, and hope for the best.
FDR, Truman, and Eisenhower wanted a national worker's medical plan (private companies insured against loss by federal reinsurance monies), but Congress said no. Medical coverage wasn't added to social security until 1965. Back then the annual $1700 Part B premium was ... ready for it? ... $72/year.
But more people in the USA have better medical care now than ever before.
OK - back to my cave.
Tom M.
'PS - the companies doing the brochures and calls get payments from Medicare to help cover their non-Medicare expenses.