Planet42 : nightmare in obtaining address details and cancellation of contract

I have tried on all communication channels to cancel this contract with Planet42, after having paid diligently for the last 25 months without skipping or defaulting on a payment. This has been a nightmare to get this contact cancelled, acknowledged and to get the car returned to Planet42. They keep avoiding my question for a physical address of Planet42 where i can return this vehicle. Instead they keep sending threatening messages for payments?? What is so difficult to understand that I have requested cancellation of this contract & wanting to return the vehicle to PLanet42? is it a ***** business where you guys actually don't have an existing dealership & want to keep clients stuck in contracts for years on end ??