Looks like EE is suffering from a national network outage that is affecting most of its contract customers, the issue also seems to be effecting its support and it customer service numbers.
My own EE service dropped over 2 hours ago and is yet to come back, luckily I have WiFi as otherwise my phone would be useless. The issue seems to have begun around 6:40pm this evening. EE has published the following tweet:
From the news I’ve managed to gather from friends and family it seems to only be effecting those on EE and not those who are based on an old Orange or T-Mobile contract.
If more information comes in we will be sure to update you.
Are you one of the affected customers?
Source: EE Twitter & my own EE service
UPDATE: EE have confirmed service is now fully operational as of around 9am on the 20th of March.