Hi, if you want to do BBA after doing diploma you have to go for lateral entry. There are some exams that you can give in order to get into best colleges for BBA. You will also need a good percentage in your diploma as those percentage greatly affect your chances of getting into a college.

1. CET BBA - It is a national level exam.
2. SET 2020 -  This is Symbiosis entrance test
3. AIMA UGAT - National level exam
4. DU JAT - National level exam
5. NPAT BBA -  NPAT BBA entrance exam is the gateway for the admission in BBA program.

Hope this helps, if you still have doubts feel free to comment.