It happened to my grandmother. She tried to switch from Oxford to AARP because a representative convinced her that AARP had better dental, and that representative misfiled her information. She ended up losing her Medicare as well, and went without insurance for half a year while she was listed as participating with both plans, they were also both inactive. (Note, if an insurance company can hire representatives who speak other languages, then they should absolutely hire support staff who speak the same languages). She tried to take care of the issue herself, but all three spoke only English and Spanish. She had help writing letters, but she couldn't answer any of the resulting phone calls.
It took me only a day to take care of it.
Many immigrants have probably faced similar situations, but because they didn't know anyone who had the time and fluency to help, they gave up and went without insurance.
It's something to think about.