My office is located in a cellar. Cell phone reception there was very bad; impossible to make a call or browse Internet without interruptions!
Following the advice from Julie, I ordered a 3g repeater to amplify the 3G signal of Vodafone and EE.
A few days later I received the device.
Installing it was very simple (less than 10 min).
As soon as the device was connected, I got immediately 4 to 5 bars on my phones. From now on,the connection is perfect.