There is no telephone country code +857, nor 00 857. It is an unused country code.
(The plus sign means "insert your international access prefix here." From a GSM mobile phone, you can enter the number in full international format, starting with the plus sign. The most common prefix is 00, but North America (USA, Canada, etc.) uses 011, Japan uses 010, Australia uses 0011, and many other countries use different prefixes.)
Country code +856 (dialed as 00 856 from many places) is Laos.
(The plus sign means "insert your international access prefix here." From a GSM mobile phone, you can enter the number in full international format, starting with the plus sign. The most common prefix is 00, but North America (USA, Canada, etc.) uses 011, Japan uses 010, Australia uses 0011, and many other countries use different prefixes.)
The country code and area code of CÌÁdiz, Spain is 34, 856.
The country code and area code of Attapeu, Laos is 856, (0)36.
The country code and area code of Bokeo, Laos is 856, (0)84.
The country code and area code of Huaphanh, Laos is 856, (0)64.
The country code and area code of Loungprabang, Laos is 856, (0)71.
The country code and area code of Oudomsay, Laos is 856, (0)81.
The country code and area code of Pakse, Laos is 856, (0)31.
The country code and area code of Phongsaly, Laos is 856, (0)88.
The country code and area code of Savannakhet, Laos is 856, (0)41.
The country code and area code of Sayabouri, Laos is 856, (0)74.
The country code and area code of Xekong, Laos is 856, (0)38.
The country code and area code of Thakhek, Laos is 856, (0)51.