1. Are you in possession of acknowledgement given to you by the company for having received your original documents?.
2. Were you issued a relieving order, when you left the company?.
3. Did the company provide you any specialised training in India or abroad?.
4. Assuming that the company did not provide you any specialised training, you can send a legal notice to the management of the company to return your certificates, without your paying anything to the company.
5. If there is no response from the company for the legal notice, inform the same to the Labour Commissioner to intervene in the matter and settle the matter in your favour.