PPI claim is a sequential process that involves several stages. Firstly, you should write formal PPI claim letter to your policy seller. In case, you receive negative results then contact financial ombudsman services to complete PPI reclaim process. Here, you should keep patience as the process may take more than 12 months to complete the task. It is also important to acquire full information about the process before starting it for success of it.
Reference: PPI Reclaim