105 Medicare nightmare

My mom got a bill for $22,000 from Medicare saying they were NOT covering my dad's angioplasty/stent/stint (however the hell you spell it--I can't even get 2 people to agree on how to SAY it) . Their reasoning? My mom has a job and therefore has other insurance. Which she hasn't for 2 years.
Like a dutiful daughter I went over yesterday and called Medicare.
Can I give you some advice?
DON'T ever call Medicare.
A polite recorded voice told me there was high call volume and all representatives were busy and I might have to hold for a while. Fine. The voice then suggested I call back at another time, and gave me some options. I held on. The voice said again that all representatives were busy, suggested I check the Medicare web site for help, and then hung up on me.
This happened three times. I was on hold various times, from a minute or two to close to twenty.
Total bullshit.
So I went downstairs, went to the Medicare web site, and they have NOTHING. No contact form. Everything directs you to call the SAME number that just told me to check the website instead and hung up on me.
I hate government. I've voting today. Any incumbent, I've voting out. No one could be worse than who we have now.
As far as my dad goes, he's been really quiet. He asks me all the time "when are you coming again?" and I tell him the date and time, he looks at his watch and says "what's today?" So I'll explain. "Today's Friday. I'll see you at 5:00 on Sunday at Grandma's for dinner." "Okay." He shakes my hand, pats me on the shoulder.
One day recently, when I was explaining when I would come over again, he said, looking sad, "You're really busy, huh." It makes me feel so guilty, like I should move back into their basement. Yeah, like that would work. But then on Friday when he said "When you coming again? About a week?" and I said Sunday, he was happy.
But when I went over yesterday to call Medicare, he didn't even come and talk to me until I was leaving, and then he only waved.
A couple of weeks ago, I went over on a Wednesday night for dinner and then stayed to do a puzzle. My mom decided to take the dog for a walk. My father got very upset. "I don't like it when she's not here," he said to me, prowling the house. "I don't like it at all." I explained that he wasn't alone, I was there with him, but that didn't matter.
However, my mom was surprised when this weekend, he was talking to someone on the trail where they were walking with the dog, and he said "my wife" (he doesn't know her name, though--she's "hey" and "they"). My mom said he was trying to talk about me, but he couldn't remember my name or say "daughter". So I guess he does know who we are, to a certain degree. But he doesn't respond when I call him "dad" anymore so I call him "Bob."