Upgrading IOS Mobile App

I have an Existing Android App which is 100% completed and IOS app which is 80% completed. I am looking for a dedicated and committed developer who can Upgrade IOS App, do payment gateway on both Android and IOS , do chat options on both Android and IOS Apps . This would be first phase of the project. Second phase would be other functionalities which would be required in both the Apps and Annual maintenance contract for both the Apps Android & IOS.