I'm sorry to hear about your situation. If you have already written to the principal and HOD without receiving a response, you may want to consider reaching out to the college's administration office or student services department to inquire about the process for obtaining your certificates without having to pay full fees. Additionally, you could also consider seeking advice from a student ombudsman or a legal advisor who specializes in education-related matters. It's important to approach this matter with patience and persistence while exploring all available avenues for resolution.