Where is telephone country code 0018?

Telephone country codes never begin with zero.

Telephone country code +1, dialed as 00 1 from many places, is North America (USA, Canada, etc.); you need the next three digits to narrow down the location any farther.

Telephone country code +8, dialed as 001 8 from many places, is an incomplete code in eastern Asia, or possibly an international telephone service. You need one or two additional digits to begin narrowing down the location or service.

To reduce the possibility of confusion with international telephone numbers, it is best to quote the number beginning with the single plus symbol and the correct telephone country code, omitting any dialing prefix.

(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.)