ATTBI refuses to do reverse DNS?

A client of mine just discovered that he could no longer do ftp transfers to my machine. His IP address had changed to one in 12.240.20 and there is no reverse DNS for that block. His previous assignment was in a totally different block which did have reverse DNS. Calls to ATTBI got the answer that they are not obligated to provide reverse DNS and have no plans to do so. My servers refuse connections when there is no reverse lookup. Is this common? -- I suppose I could set up a bogus reverse for him, but, feh... -=[L]=-