Bad Customer service

I had a very customer experience with Arkamens bochum plaza after I purchased a phone from them. Few days after I purchased the phone,it was not picking up any network.i took the phone back they said they will hv it checked. After 3 full weeks waiting for phone I finally get my phone.this time they give it to me with a sim that isn't registered. I've spent a lot going up n down because of this. I no longer want the phone but ask them nicely to refund me.