count max quantity calls on hold

Need help with DAX.

I have a table from a Call Center company, where people call and ask for support.

I have the date and full time (including seconds) when a call starts, ends, and total time on hold (waiting for an available attendant).

My dashbard is shown in periods of 30 minutes.

I need to know, in each 30 minutes, what is the maximum quantity of calls on hold.

Lets say this company only have 3 lines to receive calls.

In the image below, showing a full 30 minutes period, rows 1, 2 and 3 are active calls.

Row 4 starts on hold (dashed line) and the call is active only when row 2 ends.

Row 5 starts on hold (dashed line) and the call is active only when row 1 ends.

Row 6 starts on hold (dashed line) and the call is active only when row 3 ends.

Column A is only active calls.

Column B is 1 call on hold.

Column C is 2 calls on hold.

Column D is 3 calls on hold.

Column E is 2 call on hold.

Column F is 1 call on hold.

Column G is only active calls.

In this example, I need to show 3 as the maximum quantity of simultaneous calls on hold ( column D ).

It is not the distinct count of rows 4, 5 and 6.

How do I do this?