Hello dear Student, 
You don't need to worry about this.
There will be no problem in future if you take pcm now and want to study commerce or banking in future , that is graduation.  You will be allowed to take commerce or banking if you want to take pcm now.
thankyou
Feel free to ask your further queries if any

Hello ram sir, you can for doing banking course! Both the fields are too different things! But yes you can give the banking tests where you need to qualify.. for banking exams it is required to have a good general knowldge and also you can refer to the banking books if you require! These books are specially ment for clearing the banking exam .. you may refer to those books! 

All the best