Voluntary Termination of my car

[Guest]

I have sent an emailed letter to the finance company requesting to VT my vehicle and received a call to discuss. They agreed on the phone that I was in my rights to do so. This was over 4 weeks ago and have sent several emails asking them to pick the car up or give me details where to drop the car off. I have not received any further call or information from them what can I do now. Also when do they calculate the excess mileage payment from is it when they collect the vehicle or the date I sent the termination email. I ask as obviously it is in my interest the longer it goes on the pro rata date reduces my bill and so am I in my rights to take the date from when they pick the vehicle up.