Five years of continuous service is the eligibility for Gratuity.
Even though your employer had changed the name of the company for the purpose of Gratuity they should consider old employee's service as continuity of service. However if there is a break-in-service between two companies employment with new employee number and PF number Employer can deny gratuity openly.
The change is company name does not affect your eligibility for gratuity provided you have worked for 5 years. Please take your appointment letter, salary slip, PF statement from 1 st month of your service and approach the Labour Authorities in the area where your company office is located. They will further guide you as to how to file the complaint with them and then they will call the employer for further discussions.
Adv. Manish Gadre
As mentioned by Shri Laxminarayanan if the company has given new appointment with new PF Account, you will not be in a position to prove that you were with the same company for over a period of 5 years and above.