Nearby registered restaurants

Hello,

Can someone suggest a Xamarin Forms code to display ONLY the registered restaurants (registered with the app) specific to the customer's location (preferably, within 5 km range or so)? Google API rest webservice shows all the restaurants, which is not applicable in my scenario. I want to filter out those restaurants that have registered with my app.

Just to add, I actually don't need the map. I just need textual data, information like name, address, phone, and distance from the customer's location, etc. 

Thanks in advance.