Salestrail does not use a lot of data at all, but requires a network connection as most of the mobile applications, otherwise, the phone bill will be impacted very insignificantly.
2. Offline calls
You can use Salestrail from any location as long as the location provides a decent internet connection. All the operations are done on an on-demand basis.
For Android users, we use an offline-queue to store a call, and after going back online, they will be automatically logged. However, for iOS users, due to Apple's restrictions, after going back online calls will show up in unlogged list first, and they you can click to log them from the app.
Emails and Meetings are processed in the Cloud regardless of internet connection.