VOIP dialer app for Android and iOS

I want a customized dialer for VOIP app to app and app to PSTN calls. Subscribers will sign up online and then use username and password in the app to log in. I am looking for someone to use an SDK library like liblinphone to design the VOIP dialer app. It's OK if you can do it with any other library that is not libliphone as long as the job is done. The app will be for Androis and iOS. I want GPS and SIP headers to be added to the app. The GPS will send location of caller to server because I don't want, for example, a caller in Kenya making app to PSTN calls. Since the app is going to be used in different countries, some countries are restricted from certain operations (like app to PSTN). The GPS is to be used to determine location. The app will also be used to serve country-specific advertisement. I don't want to serve announcement or tips meant for Ghana to someone in Kenya or Tanzania. Geo-location is necessary to do that. Other things include color, logo, and so on. Please you can download and look at Zoiper, Linphone, Simple Caller and check how they work. PLEASE DO NOT RESPOND IF YOU DO NOT KNOW OR CANNOT AND WILL NOT BE ABLE TO DISCUSS WHAT YOU NEED TO DO AND HOW. Ignore price listed. We will discuss price in detail. Thank you.