The ping monitor Taf has referred to above is a way of monitoring your connection 24/7. It is done by a third party which constantly sends messages to your router to respond to (doesn't affect your connection) and if your router doesn't reply (like when your connection drops out) then it knows. When you have got an intermittent fault you need information like this to show a VM tech when he comes to your house so he can see something is wrong and try and work out what is causing it.
Your graph will look like the one above but will be more colourful if you are having problems. If you experience any disconnections they will appear as a solid red line vertically on the graph. The good news is that although the graphs only show one day at a time, they are logged so you can go back months and retrieve them so even if you only start the monitor today, you'll have plenty of evidence if you can't get a tech out till next week for example.