Sony Xperia Z5
James Bond uses a Sony Xperia Z5 mobile phone in SPECTRE.
The phone can briefly be seen in the Aston Martin DB10, when Bond calls Moneypenny while being chased by Hinx. It's not 100% confirmed if Bond uses the Z5 or the smaller Z5 Compact.
According to Sony the phone is the Xperia Z5. This model is also available in the smaller 'compact' version, it is not confirmed yet which model is used by Bond.
For other countries, ask you local phone store for the Made for Bond edition of the Z5, which should come preloaded with some Bond sounds and images, and in a special SPECTRE box.
The phone can also be seen in a Made For Bond commercial starring Naomie Harris as Moneypenny.