Like I said, I get why its frustrating…and yes this is why you should recheck and recheck again all those confirmations. I feel like it is also a case of poor customer service; because there should be a way to fix that. I know my employer as a record keeper of H&W does in fact do for us as participants.
Its not bunk, there are guidelines as to why there are windows for annual enrollment, and restrictions on time frames even for open enrollment around life events.
I wish the process with your provider was better and more flexible.