Add features in PHPJabbers framework project

I have a car rental scrip purchased from PHPJabbers that needs modifying. I need to include 3 new features on the current code: 1. Coupon Code So we will have to have access to create a coupon code feature and be able to input the discount in % or amount in dollars . We need to create the coupon code and link the code to the specific discount. 2. Calendar fixed per vehicle type: There are different types of vehicles: 1. cars 2. campervans 3. motorhomes. In the car section the systems charges you hourly. lets say if I book from the 1st of July to the 3rd of July it charges me 2 days, that is fine, which is how the system is configured now. We need to able to add new type of vehicles e.g. campervans, motorhomes and on those the system should charge you full day calendar. 3. Enter rate manually when doing a manual booking. When I go on the reservation tab and then +add reservation (will happen when staff member will take booking over the phone) I should be able to overwrite the rate manually, set up previously on types and rates as sometime we will modify the rates on especial circunstances - All features should be able to sync with the rest of the internal system. Thanks