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.)
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 01134 code in the UK.
There is no area code 20 in the UK
The country code and area code of Baja, Hungary is 36, (06)79.
The country code and area code of Gulmi, Nepal is 977, (0)79.
The country code and area code of Jalingo, Nigeria is 234, (0)79.
The country code and area code of Navoi, Uzbekistan is 998, (8)79.
The country code and area code of Aberdeen, United Kingdom is 44, (0)1224.
In the UK, 0121 is the area code for Birmingham.
Cambridge is in area code 01223, or +44 1223 from outside the UK.