According to Baidu law, if you forget which insurance company bought the mortgage insurance, you can take the following steps to try to retrieve the relevant information and surrender it:

1. Looking for an insurance policy: If you still have relevant documents or insurance policies for mortgage insurance, you can refer to the insurance company information in the documents to confirm which insurance company provides the service.

2. Contact the bank or lending institution: If you purchase mortgage insurance during the loan processing, you can contact the bank or lending institution that provides the loan to consult and confirm the information of the insurance company that purchased the mortgage insurance.

3. Check the bank statement: You can check the past bank statement to see if there is any payment record for purchasing mortgage insurance. Insurance expenses are usually shown on the bill to help you identify the insurance company.