Hard reset t20p

Good afternoon to my home phone connected remotely and changed the password. Service providers of telephony, I do not use bought the phone in the store. As the calls started coming in large numbers. Tried to reset to factory settings. Pressed the OK button in 10 seconds, but after that it asks for a password, which I don't know. How to solve this problem?

Yealink T20P
Firmware: 9.73.193.50