How to unlock an encrypted cell?

[AC Question]

My cellphone (Moto G4) is encrypted, and I changed the security from password to PIN. I had to restart my phone and asked me for a PIN which I remember very well but the cellphone does not accept it. I also remember the password I used to use but the keyboard to initialize the phone is only for numbers, and I have not the opportunity to type letters to try the password instead the PIN that does not recognize. I used the PIN many times to unlock the phone and it works. But for initialize the OS doesn't. How can I try typing letters? Or what can I do?