We bought our son a monthly contract for Xmas with unlimited calls/texts and 1G data, we want to prevent getting huge bills when he uses his allowances up, can we get a block when they are reached or do we just have to maintain/monitor through the 75% & 95% of limit notification texts we get from Virgin?
Some handsets have data limits in the settings which you can use. I'm not 100% if this will stop data being used but it'll give you a notification to see if you're about to breach it. Please provide the handset model and we can check further.
Lee_B has also advised on our App which you can also use to monitor data usage. More information on this can be found here.
If he does exceed his allowance then you'll be charged at the rates shown here. Look for the sub-heading which says Data.