Start by making a formal complaint to the bank or savings provider, explaining what happened, the impact on you and how you would like it resolved. Keep copies of your messages and supporting documents; the firm will usually have up to eight weeks to issue its final response. If you remain unhappy, or do not receive a response, you may be able to take the matter to the Financial Ombudsman Service, normally within six months of the final response. Check the firm on the FCA Register and contact Citizens Advice if you need help understanding your options.