1001 Pay system

We need website and app for ios and android. Our aim is to announce price list to users. Price will be changed by operator, so expect users can receive notification. We already have web host (windows) and registered domain and ssl and mssql. Using C# and Xamarin and web services is preferred. Current Version (basic) requirments: 1- User just see mainpage and price (buy/sell) list of products.(no need login) 2- Operator have one page to add (edit, remove) products and update (buy/sell) prices. Product has just Name property.(one operator) 3- Prices better not be overwritten and keep history of prevoius prices. 4- Updating prices should be notified to users.(usually twice per day) 5- English Interface and user friendly. 6- I would like to publish apps officially on app store and google play 7- Users view statistics colaberation in UI design and Database is kindly requested. Next versions requirments (Just for your information): User profile, price according to user classification, multi operator with access level and premission, view price history and changes in chart, input users deals by operators, multi language, using Sms verification, users see activities of themsleves after login & etc