Batman, you were probably right if you request the deletion from Alamy first. I deleted all the keywords, title and discriptions first and then request the deletion, that was how it should be done. The image will disappear after 6 months, but it would not be searchable within days. Alamy didn't raise any objection over that.
In Alamy, although you have to wait for 6 months for the image to disappear from the database, you can delete all the keywords and descriptions so the image will not be searchable anymore.
Bigstock will delete for you, if you email its support.
freedom, i don't think you can change the keywords, it's greyed out !