Where the initial query is not resolved to your satisfaction, or if you wish to make a complaint, you should submit a formal request to firstname.lastname@example.org.
Once we have received your complaint, we will acknowledge receipt within three business days by email. We will aim to resolve your complaint as soon as possible and in any case no later than eight weeks from the date the complaint is received.
When investigating your complaint, we will consider the subject matter of your complaint, the evidence you have provided, the evidence on our records and relevant guidance from the regulator, the Financial Conduct Authority (FCA) and the Financial Ombudsman Service (FOS). We will write to you setting out the outcome of your complaint and supporting reasons, including details of how we have calculated any redress if applicable.
For further information - https://www.fca.org.uk/consumers/how-complain