An ISP problem with DotNetNuke portals

For the past 2 years I’ve maintained several sites through a DNN portal until my ISP recently made changes which made them disappear.

The DNN portal mechanism redirects domain names to discrete folders giving the appearance of independent web sites.

What now happens is that all 6 domains map to the main directory of my DNN structure.

After a week of trying to explain the issue to my host, who provide DNN as a hosting feature, I’ve asked them whether they’ve referred the problem to DotnetNuke tech support. At this point they stopped talking and I’m faced with having to backup my sites and restore them on another ISP.

Does anyone consider that the ISP has an obligation to fix my problem, or aat least help me get it back online on another host?