Parents dropped by their Medicare Dual Advantage plan. Any advice?

Just posting this because I am at my wits end and feeling like I have nowhere to turn to. I am 38 years old, single and have had my parents move in with me at the beginning of this year because they could no longer afford to live on their own and my mother alone could not care for my father who has had worsening dementia over the years.

I had no idea how Medicare and Medicaid worked and found out the hard way when both my parents lost their Medicaid coverage due to the change in address. They moved from NYC to Westchester County. I notified SSA of the address change for both of them and with the help of a social worker who works at the adult daycare center they attend, my parents were able to get Medicaid coverage back in Westchester.

Fast forward to October of this year, my mother sustained a burn on her foot that required her to go a wound care center for weeks. Last week Wed. 11/30 we were told that she would need to get a debridement and possible toe amputation. She was started on oral antibiotics. On 12/1, I was told that my mother needed another antibiotic. When the script was sent to her pharmacy, the pharmacist called us to tell us that she was no longer covered by her plan. Alarmed, I called Empire and found out that she was disenrolled on Thurs. 12/1 from their dual advantage plan due to "no longer having Medicaid or a qualifying level of Medicaid per state contract" and that Original Medicare would be covering her starting that day. The "enrollment specialist" told me that a letter was sent out in August stating these facts. We never received this letter, possibly due to the move. I told this rep that my parents have been receiving benefits through Medicaid such as attending an adult day care center and home care so it is not possible that they wouldn't have Medicaid coverage. He verified that this was true by calling their verification department and verifying both my parents' Medicaid coverage by a 3 way call with me. He then said he thinks that there was an error and tried to contact a customer service rep but was not able to. He told me that his best advice would be for me to contact the local Medicaid office and have them send information about my parents' active coverage to both Empire and Medicare. I told him that I can't undersand why that would have to be done since he just verified it with the verifications department. At this point I was exasperated since I had spent hours on the phone being transferred from one person to another to another. I thought that since the letter Empire sent stated that she would be covered by Original Medicare I didn't really think too much of it and would contact Medicaid later as it was already almost 8pm.

Monday 12/5, my mother and I went to the hospital to be registered prior to surgery. They needed to verify my mother's insurance and we handed over her Medicare and Medicaid cards. Medicare still said my mother's insurance was the plan through Empire but they still did the surgery and my mother was recovering well. The plan was for her to be monitored overnight and get a wound vac and possibly a midline for IV antibiotics.

Tuesday 12/6, I am told that the hospital is still having trouble with my mother's insurance. Medicare is still saying she has Empire. I called Medicare who said that they haven't been notified that my mother was disenrolled from Empire, the coverage still shows as ending on 12/31. They tell me to call Empire and to have them send updated information stating that her coveraged ended on 11/30. I called Empire who told me that her coverage ended 11/30 and the information gets automatically sent to Medicare. There is nothing they can do, call Medicare. Medicare tells me to call Empire.

So now my mother is stuck without any plan, while still having active Medicare A&B coverage but Medicare not covering her current treatments because they have Empire still listed as her coverage until 12/31. I don't know what to do. Any advice?