See it's all your choice, you are asking to change the field. If you are really interested in management then you are definitely welcome to do MBA but don't make your choice because you are not able to clear 2nd round of C.A.

You need to figure out your interest and choice. Getting enrolled in a top reputated college for pursuing MBA is itself a tough task with a very long process. Anyhow as you have done B.Com so you have some advantage as these colleges gives a little more preference to non engineers. Also as you have already done b.com so you will be more easily be able to connect yourself with the course structure of MBA program.

Regarding your decision as I mentioned earlier if you're interested in management course then without any doubt you can go through it. Within my batch in IIM K there were 3 batchmates who had completed C.A. worked for a few years in a reputated company as an investment banker but came to do MBA because of their interest so there is nothing wrong with your decision.

All the best!!