It is very difficult to find job after completion of 12th. Even call center demands a basic degree. This is the age where you can concentrate more on studies. Trust me, once you start working your life will be too bored, coz you are going to do the same thing in the upcoming years. I haven't come acrossed even a single call center employee who claims that he/she likes the job. Almost every such employees would have been enrolled in any part time courses. So study first.

Hi, As per my suggestion you should not opt for any job and choose to complete your education first.

In which field you have passed your 12th and what are your interests?
Any reason you prefer working?