adding up to what has been said, you cannot transfer a vehicle's registration from one city to another... a registration number, once allotted, remains with the car, as long as it lives...
also, if the vehicle is Karachi registered, then your token payments would also have to be made in Karachi... and if the car is being taken out of Karachi, then an NOC would have to be obtained from Excise & Taxation, which in turn would result in them accepting the token payments made by you in any city!!!