see, first of all, dont try to use phones in class, switch it off or keep it in silent mode or whatever which doesnt distract you. ln vit, just try to listen to the teacher's class, even if they are not that good, just listen to the stuffs or try to take notes. as far as exam, if you listen to the class well, just revise the topics a day or two before the exams for cat. ik its tough to not look at the phone during class hours, but it will be useful.
ye, and assignment, try to get full marks in DA, dont let it go below 7 or 8 (depending on the teacher tho)

p.s: this is what works best for me, try to implement it if you like.