Where in North America is area code 766?

Country code +7 is shared by Russia and Kazakhstan. There are currently no valid numbers beginning with +7 6, but that numbering range is reportedly reserved for Kazakhstan.

(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.)