Doogee complaint: Broken s61

I originally bought a phone from Doogee via eBay last June,it arrived damaged, IE the back panel wasn’t attached. I contacted Doogee and they told me to glue it back together and my guarantee wouldn’t be affected, they offered me something close to £30 refund so I agrees. The phone has never worked properly, the screen input used to lock up son I had to reboot the phone constantly, after itwo months it stopped working completely, the phone lights up and is in perfect condition other than the dead screen input. I contacted Doogee again and after many many messages they accepted for me to post it to china and wait for three months, I had to pay the postage to China and then the phone was returned to me on exactly the same
faulty condition. I’ve tried to contact customer service but the just passe back to the Doogee seller on eBay they did message me back last week and agreed to replace my phone but because of depreciation they wanted more money, I told rhen i wasn’t happy having to pay again so now they are ignoring me completely, i spoke to customer service and they said I need to deal with the seller. They are blanking me totally now.
Kind regards Wayne conley