htc phone factory reset the phone

[AC Question]

got this htc phone from a old guy and he factory reset the phone with me but then when i try to set up the phone from the setup screen its asking me for a gmail account,but when i put in my gmail its telling me to put in the gmail that was set up before,and i dont know what to do. because i lost the guy that i bought the phone from cell number. is there a way i can just erase the guy gmail and just put in mine

 

[B. Diddy]

Welcome to Android Central! Are you sure it isn't a Samsung phone? That can happen due to Knox after an unauthorized reset.