@Ljiljana23 Well, technically this shouldn't happen- the host doesn't deal with the payments at all, Airbnb does. Airbnb holds the guest's money and only releases it to the host 24 hours after a guest checks in. As long as the host officially cancelled, (as opposed to just telling you they need to) you shouldn't see the second payment charged and you will be issued a refund for what you have already paid.
But if you are wary and want to set your mind at ease, you could contact Airbnb to make sure it will all go as it should.
https://community.withairbnb.com/t5/Help/Contact-Airbnb-A-Community-Help-Guide-UPDATED/td-p/413245
Scroll all the way down in the topic post and you'll see a list of phone numbers- there's one there for Australia, if that's where you are right now.