Dial 999 on ANY mobile phone that has power; regardless of whether it thinks it has a signal. 

Then you will either :-

1. Get a connection, then ask for the police, ambulance, fire or coastguard as appropriate.
2. You do not get a connection. Find a place with a landline phone and use it. Don’t waste time trying other mobiles as none of them will work in this situation.

There are, of course, specific mobile apps for calling the emergency services; this guidance does not cover those as they change in scope and usefullness over time. The above guidance will always work.

And of course only phone the emergency services if the need is a genuine emergency.

Background :-

• If you get a connection this means there is a mobile network signal in the area; it just may not be the network that the mobile phone is subscribed to.  For emergency calls the network operators have to allow their networks to be used by anyone as a condition of their operating licence.
• If you don’t get connected this means there is no signal from any operator at all.  Then no mobile will work in that location.

Additional information :-

1. Location. In some circumstances the emergency service will be able to determine your location. This can be derived from a mix of the location of mobile phone masts, your GPS location and nearby Wi-fi networks. Don’t rely on this and try to give as much information as you can. GPS devices (such as Garmin) can show the longitude/latitude which may be useful.
2. Texts can only be sent on your operator’s network; if you have no signal for your operator you can’t send a text.
3. 112 and 911 can be dialled as alternatives to 999.  Any of these three numbers will also work anywhere in Europe and North America (US/Canada).
4. You can make an emergency call on a locked phone – on the lock screen where you enter the PIN there should be a button to make an emergency call.
5. If there is no signal for your operator you may see “Emergency calls only” displayed on your phone.