Calculating concurrent calls in a call center

Hello everyone. Need some help on how to calculate concurrent calls based on the data that I have. I've calculated the duration and start/stop times but need to know how many concurrent calls are going at any given time. Please check the attached spreadsheet.

Here are the formulas I've tried but doesn't seem to work.

=SUMPRODUCT(--(B5>=callStarts),--(B5<=callEnds))

=SUMPRODUCT(--($B$2:$B$30000<A2),--($E$2:$E$30000>A2))+1