In some cases - especially if the device has got a 3rd party logo - you will need to enter the APN settings for your chosen mobile network in order to make it work.

Here is a list of the most popular SIM cards providers:

4G LTE APN SETTINGS:

Everything Everywhere / EE 4G APN
APN : everywhere
User Name : Leave Blank
Password : Leave Blank

if not try ...

APN : everywhere
User Name : eesecure
Password : secure

 
O2 4G APN Settings
APN : idata.o2.co.uk
User Name : vertigo
Password : password

APN : mobile.o2.co.uk
User Name : o2web
Password : password

Vodafone 4G APN Settings
APN : internet
User Name : Leave Blank
Password : Leave Blank

3G APN SETTINGS

O2 APN Settings
CONTRACT
APN : mobile.o2.co.uk
User Name : mobileweb
Password : password

APN : mobile.o2.co.uk
User Name: vertigo
Password : password

PAYG
APN : payandgo.o2.co.uk
User Name: vertigo
Password : password

APN : payandgo.o2.co.uk
User Name: payandgo
Password : password

If you encounter issues try the APN without user name and password.

Vodafone APN Settings
CONTRACT
APN : internet
User Name : Leave Blank (if not try user name and password as web)
Password : Leave Blank

PAYG / Pre Pay
APN : pp.vodafone.co.uk
User Name : web
Password : web

T Mobile APN Settings
APN: general.t-mobile.uk
Username: user
Password: pass

if not try ....

APN: general.t-mobile.uk
Username: [Leave Blank]
Password: [Leave Blank]

3 network Mobile APN Settings
APN : three.co.uk
User Name : Leave Blank
Password : Leave Blank

If you are using DYNDNS the following APN settings Three mobile will allocate you a public IP address.

APN : 3internet
User Name : Leave Blank
Password : Leave Blank

Orange APN Settings
APN : orangeinternet
User Name : Leave Blank
Password : Leave Blank

If you are using DYNDNS the following APN settings Orange will allocate you a public IP address.

APN : internetvpn
User Name : Leave Blank
Password : Leave Blank