How to add up a column of HH:MM:SS

I am looking at my talk talk phone bill. I downloaded it as a CSV, re=adjusted the column widths and saved it as an xlsx. The sheet was set up as custom for the times of calls. I tried to convert them to time. I ten hi-lighted all the calls down to below the last and clicked on sum. It doesn't work. I am attaching it for someone to tell me where I am going wrong.

Thanks

Attached Files

	MyBill.xlsx (11.7 KB, 10 views)
	MyBill_Dosnt_add_up.xlsx (12.1 KB, 10 views)