unlock icloud accaunt

Hello. I bought a phone that was previously used. Made a reset. Unfortunately, now the phone is locked because it was tied to an icloud account. The former phone does not remember icloud account data. The paint on the check was completely erased, only white paper remained. The phone was purchased for a long time. There is also a box and various inserts to the phone. He used this phone for 6 months. Model iphone 6 plus? 16 gb. Can you help me with the unlock?