I have had Virgin Media broadband for 5 years, from when I was with Telewest and have been very happy with it.
I only had one problem, when I could not get online. I phoned up and wouldn't take no for an answer until they agreed to send an engineer, he found a fault with the cable outside my house and since then it's been fine.
You are paying for the service, ring them up and insist they sort it out. Try to ring during the day, you are less likely to get the Indian call centre.