I have done 3 years Polytechnic Diploma in IT in 2006. How do I get admission in BSc IT?

Yes, it's possible to pursue a BSc IT after completing a 3-year Polytechnic Diploma in IT, potentially through a lateral entry program, allowing you to join the second year of the BSc IT program. 
Here's a more detailed explanation:

Lateral Entry:
Many universities and colleges offer lateral entry prog