I have had this issue for a year so many phone calls googled the hell out of it. Customer service have no clue and take you round in circles suggesting its your devices. If the issue is on every device the problem is with virgin media.
Factory resting the router worked a couple of times. Ringing sometimes temporarily solved the issue but not for long. Probably as you can see from other posts the only other suggestions are changing dnd settings on every device, or buying another router and putting vm one into modem mode.
All of which you shouldn't have to do as you are paying for a service that does not work and is a security risk, not family safe and certainly doesn't keep children safe online as virgin advertise
My advice would be to write formal complaint through their online form, report them to ofcom and just switch providers to save yourself a massive headache