Do I have to sign for a reminder letter?

The collection letter received was not sent by the bank, but by the collector of the third-party collection company under the guise of the bank. Generally, after three months overdue, the bank will entrust a third party to collect the company's collection. In order to make the overdue repayment, the collector usually writes some serious consequences in the letter. Many overdue friends have received similar letters. Actually, there is no need to sign this letter.