I can tell you that once we started getting our SS checks, the Medicare Part B premium of $140.00 (back then) which is now $185.00 (again apologies for giving you last year's premium) was automatically deducted out of our SS checks before ever seeing a dime of it.
We pay the remaining premium of $70.00 directly to our insurance carrier. I have no idea why the premium is split like that, as Mugwumps is right - Advantage plans are through private insurance carriers. The correct amount we pay, together, monthly is $510.00. (I hate automatic payments as ours is set up - its too easy to lose track). There are more expensive Advantage Plans than the one we selected, and they have better coverage on certain things. It all depends on what you health is and what your needs are.
Mugwumps is also correct as far as being careful with Advantage Plans - they sound initially great, but one must keep in mind what they pay for if, in the future, you end up with long-term care needs or serious health problems.
We also have Aflac. It's not an insurance plan per say and is more like a savings account that pays a certain amount for certain things, depending on what you sign up for.
I urge you to talk to a professional as I am not one. Everyone deserves healthcare and deserves to understand in full what they are paying for before they sign up for it.
Very glad to help. Thanks for the compliment.