If you have taxable sales of more than $30,000 you should already had a GST registrant number, been collection and remitting GST/HST in Ontario, to the Ontario government. If you make less than $30K this was not required and you did not need to charge your guests. However as of July 1 2022 Airbnb is charging HST on all rentals in Ontario, even for those host who do not meet the $30,000 threshold. This is WRONG but CS Ambassors do not understand the Tax laws and only read a script. I believe you need to make a written complaint once you understand your personal tax obligations ie call the government then contact Airbnb.