How to factory reset a locked iphone 6?

So I bought an iphone from a seller on eBay. It's in great condition. However, they didn't factory reset it before sending it to me so I need their pass code to unlock and use it. I've messaged the seller, no response. Searched the name on the return address and judging by pictures on Facebook and the background photo on the phone, I highly doubt it's stolen or anything like that. I think it's just they honestly forget to reset it and don't check their eBay messages very often.
so my question is, is there a way I can reset the phone WITHOUT the pass code? I've tried restoring it on iTunes but it says it can't connect because it needs the pass code.
I could message the person on Facebook, but I don't want to come off as creepy and invasive

I'm almost 23, why is my mom tracking my location on my phone?

I came back home for summer break from college. I will be 23 soon. My mother has been insufferable since being home. The first night I went out I lost my keys, and she hasn't given me keys since. Also, she tries to make me get back home at 12 am.

I do not understand the point of being home at 12 am or not giving me keys when I have been away at school for almost 4 years. At school, I will stay out until 2 am. She is also convinced I'm an alcoholic when I don't drink during the week.

She has called me every name in the book, screams in my face constantly. I also found out that she started tracking my location on my iPhone.

What is the point of this? My friends said this makes no sense and I agree. I don't get why she is being like this all of the sudden. Her fiance lives here and probably thinks I did something bad but I haven't.

IPhone charging port replacement?

I bought a phone off offer up for 200. Its great but it has trouble charging. How much does It cost to have it fixed? Or how could I replace it myself?