@L-A2400 It is sometimes better to use the message option to communicate with support. That way you can lay it all out clearly, they can read it, and it is documented.
There are tricks to dealing with Airbnb CS.
State the issue aas simply as possible, in chronological order, using bullet point, not paragraphs.
On March 10th, 2021 we made a booking for (insert name and URL of listing)
On April 1 we were offered a date alteration.
On......
Like that. Just be really clear and stick exactly to the issue, leave anything extraneous out so as not to confuse the issue.
At the end, state exactly what you are asking support to do for you- in this case it seems you want a cancellation with full refund, unless they can ensure that you still have a valid booking and with whom.