The operator is understood to have first experienced some disruption early on Tuesday morning – with service outages later spreading across large parts of the UK.
The tracking website – Is The Service Down – reported complaints first appeared on social media at 8:20am, peaking as the afternoon wore on.
Virgin has apologised “for the disruption and inconvenience” some customers experienced.
In a message posted on Twitter, it said: “This was due to a technical issue which we’ve now resolved.
“We will be compensating our customers for the loss of service and will let them know the details shortly.”
Virgin Media said the problems only affected its mobile phone services, which use EE-owned infrastructure, and there was no issue with its cable services.
Twitter users complained they had been left in the dark about the disruption, though Virgin said its team had been responding directly to complaints and had posted a statement on its website.
There was a familiar theme to the complaints – with the majority stating they had been unable to use their devices for hours.
One wrote: “@Virginmedia any news??? I’ve been offline since 11am… no calls, No texts, nothing.
“I am trying to earn a living and book in work for the week, but looks like ill have to miss out!! Thanks a bunch, who do i invoice for loss of earnings???”