Itunes

Hello,

I had someone’s itunes account on my phone last year but i removed it to my knowledge. However, I have been recently trying to update some apps and it keeps saying sign into your account and the person’s account keeps popping up. When i click the option of forget password and type in my own apple ID and verify it keeps saying unknown error occured. This just keeps happening. I talked to the person and they said its nothing they can do on their end what do i do?