Hello.
In real situation there is not any college and university that can allow you to admit in BSc course without having science or mathematics in your class 12th, as BSc name actually designate with the bachelor in science for which you compulsorily need to be from science background , even if you want to go for BSc Computer Science so here also you need to have mathematics in 12th and if you want to join BSc in physics, chem, maths and related subjects then again there need to have science in 12th , but again for this you have a chance to do BSc in  humanity subjects , like you can do BSc in geography basic eligibility criteria for this is you must have completed your 10 + 2 pattern with minimum aggregate marks (according to universities/colleges) from a recognised board.
So here is the list of some best colleges in kolkata that offers you BSc in  geography and more humanity subjects:

• Presidency university Kolkata.
• NSOU, Kolkata.
• Adamas adamas , Kolkata.
• Jadavpur  University.
• Asutosh College.
• Calcutta University.
• Vidyasagar  College ,Kolkata.
• Hiralal  mazumdar memorial College.
• Shri  shikshayatan college.

best of luck.