I am a Xamarin expert - https://programmium.wordpress.com//?s=xamarin&search=Go. I have already done a similar project. I can do this in 3 days for the given amount.
Relevant Skills and Experience
Xamarin, C#, SQLite, Azure, Authentication, Android Services
Proposed Milestones
₹3000 INR - Just app that can store recorded phone calls to local storage
₹1000 INR - Option to record calls from selective numbers
₹2566 INR - Provide a UI to manage recorded calls from the app
₹100 INR - Upload data to Cloud (or any other file server) - You should give me the URL to where to upload