Three mobile can't call Virgin Media landline

Last Thursday (4th July) I noticed I could not call my home Virgin Media landline from my Three mobile - it simple just cuts off as soon as I press Call.  Cross checked using my wife and son's Three phones to call - same outcome.  I can dial out to everyone and other users with different providers (BT, EE, Virgin (O2)) can call my landline.  It is only incoming Three calls that are the problem.  Checked with neighbours and 2 other people confirmed they have the same problem.

I call Three support who the number appeared permanently engaged to them (it isn't) but they had no call barriers in place and so it wasn't them.  Had Virgin Media engineer here this morning who also says they have no barriers in place (the usual cause apparently).

So neither company says it is their fault or will do anything more but I still can't call my own landline from a Three mobile and neither can my neighbours.  How do I get anyone to fix this issue?