Where in Turkey is area code 543?

Answer 1

Turkish area code 543 (or +90 543 in international format) is a mobile phone prefix. It is primarily assigned to Vodafone, but with number portability any specific number could be served by any carrier.

(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.)