Modification of order creation on OpenCart

You need to modify the functionality to OpenCart: (the function is designed to provide services for the dispersal of iPhones).
When ordering a service, you need to set an imei phone;
Payment is made only with loans (in case of not having enough funds, do not allow you to create an order)
- simplify the steps when ordering;
- in one order only one service (goods) or in one case without a basket
More information on individual correspondence