As "last call barring" is included in the bill, albeit "free", surely a way to force the issue of this facility being unavailable is to stop a proportion of the bill until the company gets its finger out and solves the problem. It is not complying with the stated terms and conditions and "free" only means customers have paid in a different way.
Good to hear the gentleman's voice again. Like the previous poster, however, have not yet been able to test the system fully as I did not want to bar the last caller!
Hopefully we have finally made some progress, having been without last caller barring for some weeks now.