Cancellation impossible

I need to cancel a hotel booking made for 2 nights 29th and 30th September 2017 (itinerary number ********** 625934). Being out of town last week I tried to do this on my cell phone and iPad and could not a "cancel" button on the mobile version of the website. Returning home I tried on my laptop and there is such a button! I proceeded to fill in all the details and when I clicked on "Submit" it conveniently (for Expedia) does not work! To add insult to injury I am informed as I am cancelling after 22nd September there is a 50% cancellation fee. I have had similar experience with other websites particularly ones which have an "unsubscribe" feature - often don't work either. I cant use this booking agency again. I will lodge a dispute through Amex and get my money back that way.