Phone sent to wrong return address after cancelling contract

Sometimes around April 24th I canceled my mobile subscription. The cancellation was within the time frame. Since the phone was so expensive S23 Ultra. I called to confirm what's the best way to return the phone. I was directed by a KPN customer care agent. Who gave me an address to send it to. Later I was told he gave me the wrong address. Upto now, getting the phone hasn't been successful. I now have a bill of about €155 euros to pay for a phone I have never used. And on a mistake I never made. Seems I will be paying this amount per month until the phone is found. It's sad that I have to go through this.