Telephone country codes never begin with zero.
Country code +1, dialed as 00 1 from many places, is North America (USA, Canada, etc.), and +1 844 is a toll-free code within North America. You may be able to dial the number from outside North America, but international toll charges will apply.
Country code +84, dialed as 001 84 from many places, is Vietnam.
In the UK, domestic telephone area code 01844 is Thame, Oxfordshire. Other countries may have a domestic telephone area code 01844 or similar.
To avoid confusion, it is best to write an international telephone number in correct international format, beginning with the plus symbol and the correct telephone country code (e.g., +1 or +84), omitting any dialing prefix.
(The plus signmeans "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.)
01844
Leichtenstein is telephone country code +423.
where is telephone country code 1816
That is not a country code.
Country code +57 is Colombia.
Country code 52 is Mexico.
Fiji has telephone country code +679.
Gibraltar is country code +350.
Moldova is country code +373.
Slovenia is country code +386.
Vanuatu is country code +678.
Niue is country code +683.