01612 is not an area code in its own right. The area code is in fact 0161, and the following digit is part of the local number.
So 01612 should actually be written 0161 2, although it makes no difference when dialling the number.
For more information on 0161 numbers, see the page for the 0161 area code
The cost of calling an 0161 number
When calling from a landline, calls to 0161 numbers can cost up to 10p per minute, dependent on the time of day, and there is usually also a call set-up fee
When calling from mobile phones, calls to these numbers cost between 10p and 40p per minute.
Most landline operators offer inclusive call packages which allow calls free at certain times of the day, or at all times, and most mobile companies include free any-time minutes in the monthly contract payment, or a bundle of minutes for a reduced cost in the form of a top-up credit.