If you run out of your monthly data allowance, you can still go online via EE Stay Connected. The service provides speeds of only 0.5Mbps but it means you can still use WhatsApp, other messaging services, and Maps, so the essentials are still usable. Once you're able to, you can then buy a daily or monthly data add-on to restore your full service. It's useful for emergencies as you don't miss out on messages, simply because you ran out of data.