I copy my call history into an Excel spreadsheet and save it there.  It’s a bit of a pain at first, but you get used to it.

Unfortunately that would take days because my call history only shows 10 entries per page and I would have to copy and paste 50 pages or more.

Too arduous! There must be a better way!

50 pages would be arduous.  I am a low volume user, and I try to log into my account every day to copy the activity so it does not become too much of a chore. Hopefully another user has a better solution for you.  

How do you do it? Are you able to just select the entire page of entries at one time?

Yes, I select a whole page of entries at one time and select copy.  Then go your Excel spreadsheet and select Paste.  The call information will go into separate columns (I.e date, number called, etc.) without you having to do any formatting.    I use a iPad, but with the amount of data you need to copy, you might find it easier to use a laptop.