Phone area code

Each country area has its own local phone prefix. This phone prefix is added after IDD and international phone number. In case of local call (call just between areas not countries) you don't need to add IDD and international phone number.
If you are calling from other country than Poland to the Bialystok area, dial IDD of your country, then international phone number (country code) +48, after that phone area code of Bialystok 85 and call number.
Example: International call
+48 - 85 (Telephone number)

If you are calling inside country Poland , you don't need to dial IDD and international phone number (country code) of Bialystok +48. Just dial phone area code of 85 and call number.
Example: Local call
0 85 (Telephone number)