In order to remove the line between the Title and the DayName of the RadCalendar control you could hide the visibility of the grid lines. This could be achieved when the RadCalendar.GridLinesDisplayMode property is set to Hide. Please note that in this way all grid lines of the RadCalendar will be hidden. In case you want to add a style for a concrete cell you should use the CalendarCellStyle class. From the project attached, please take a look at the MainPage.xaml and MainPage.xaml.cs files how to achieve this scenario.
I hope I could help. Let me know if you have any other questions.
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