Instead of trying to change your branch through donation, you should rather earn that place for yourself through your marks. If you have maintained a CGPA of 8.5 and above in your 1st and 2nd semester then you would be easily able to change your branch in the 3rd semester. This CGPA is a minimum criterion for switching branches.
If you are willing to change your branch to Mechanical Engineering or Civil then you would definitely have to step up your score game as there are plenty of students with a CGPA of around 8.5. One with the highest marks is generally given more preference in changing their branch at Haldia Institute of Technology.