I need 1month old call history

Call history only stores the last 100 calls, if you need more, log on to your carriers website, they usually provide a longer call history list.

It's different for each carrier, if you need help with their website, contact them and ask how.

If you begin individually deleting the calls listed in “Recents” …

… you’ll find that older calls are “pulled-up” into the display.

Keep deleting until calls from your date of interest are displayed.