If you have a lot of times to enter, it can be very tedious to have to
type the colons if you use the numeric keypad. Instead, I enter min:sec
as min.sec and then convert it into min:sec - I'll let you have the
formulae if this is of interest to you.

Other things that you might consider is to work out the rate charged
for each call type and compare this with published tariffs.

Hope this helps.

Pete