Host cancellation

If the host cancels a booking 5 months out how long does the guest have to accept or decline the new accommodation on show? 
Can the guest decide I prefer the Hilton , is there a cap on the price offered out ? 
A Booking.com agent said 24hs for property 1 then offer 2 is 48hrs if no response a reminder is sent 72hrs reminder 2 96hrs and if no response again
A maximum of €25 extra +your original booking fee will be added.

I asked him to email me confirmation of this , response was i can’t do it while we speak on the phone and it will be emailed once you hang up . Never received it of course .