Passcode 4 digit and one letter

[Hatter]

Can someone please help on passcode 4 digit and one letter needed. I have galaxy s7 and only recently using biometric and before 4 digit code... but now the phone has restarted overnight and asking for 4 digit and one letter. I've never used this before. please advise as this is my work phone 

[Sadii]

Is the phone second hand?

[AndrewL]

@Hatter: Please try signing in to Find My Mobile using the Samsung account details you have registered to the Galaxy S7, to see if you can remotely unlock the phone from here. 

https://findmymobile.samsung.com