Area code 028 is all of Northern Ireland, with 8-digit local numbers. A number beginning with 028 93 is in Ballyclare, but it is incorrect to quote the area code as 02893, because '93' is the first two digits of the local number, not part of the area code.
In international format, Northern Ireland is area code +44 28.
(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.)
UK telephone area code 028 (or +44 28 in international format) is all of Northern Ireland. A number beginning with 028 77 is in Limavady. The '77' is the first two digits of the 8-digit local number.
The whole of Northern Ireland uses the (028) area code.
Local numbers have eight digits: (028) xxxx xxxx.
Numbers that begin 79xx xxxx are in the Magherafelt, Londonderry, area.
A UK telephone number beginning with 079 (or +44 79 in international format) is a mobile phone.
Country code +44 is the UK, and +44 7926 is a mobile code, along with the rest of +44 74 through +44 79.
All UK area codes begin with a 0. There is no area code 6010 in the UK, and there is no 06010 code either.
UK area code 020 is London.
There is no area code 20 in the UK
There is no 01134 code in the UK.
The country code and area code of Jalingo, Nigeria is 234, (0)79.
The country code and area code of Gulmi, Nepal is 977, (0)79.
The country code and area code of Navoi, Uzbekistan is 998, (8)79.
The country code and area code of Baja, Hungary is 36, (06)79.
The country code and area code of Aberdeen, United Kingdom is 44, (0)1224.
Cambridge is in area code 01223, or +44 1223 from outside the UK.
In the UK, 0121 is the area code for Birmingham.