Android IPhone App Modify

I'm looking developer who can upgrade our app. I had a simple app created for myself, as a business app... Now i had a deal with a freelancer who will edit app and put in new information if i get a new client and basically change the information in this standard template with new customer information. i will supply all design, you just edit app Freelancer have to upgrade IPhone app. & if i want to upgrade my current app, with new contact detail etc. Now i can not get hold of this guy and want to edit my app. I have apk. file only and link to google play.. I have new customers who want the same thing... coming. Details send message...