Why is there a lot of black chat records?

Delete chat history: 1. Click to enter the Pinduoduo of the mobile phone. 2. Switch to the chat page. 3. Long press the record to be deleted and click Delete. Enter the customer chat status page and find "!" Symbol, click it and a drop-down list will appear, which contains three option buttons: Report, Move to Blacklist and Manage Blacklist. You can click one of them as needed to continue the next operation.