B.Sc

You have not write about the college/university name. However, the basic eligibility criteria for 3 years LL.B. Regular course is a Bachelor degree in any discipline with minimum 50% of marks for general, 45% for OBCs and 40% for SC/ST candidates. Therefore, you can be eligible if meeting the above eligibility criteria. So you have to first complete your degree requirements.

Yes, you can take admission in M.A. (Journalism and Mass Communication). The eligibility criteria is given below.
Eligibility criteria : The basic eligibility for admission to M.A. In Mass Communication is a Bachelor degree in any stream of minimum 3 years duration. It is not compulsory to have a Bachelors degree in Journalism or Mass communication but it certainly gives an edge. There is no restriction with respect to stream of education in graduation.

The criteria depends upon the college/ institute/ university you are pursuing your B.Sc. Maths programme from. If there is a process to transfer your programme to the other course, then you need to contact the admissions department of your respective college in order to change the programme.