They appear to go from a free web-based service to costing YOU money by wasting your fax line, paper, ink and time in their inquiry, plus the same in reply by you to them.  This is an additional service fee cost for sure.  I agree:  bill them for it. 

  The alternative is to get rid of the fax all together and operate only by email (get and learn to use a portable scanner and high-resolution digital camera that you can order online from Best Buy or any of the big electronics stores).  Get a free GMail or Yahoo! or whatever account and cut the cord to fax costs.  In the long run, this is probably a better solution for everyone.  Still wastes time, but at least not physical resources.