I am trying to understand my father's cell phone plan/charges and I cannot understand some of the charges (and neither can he).

He says that until the past 6-12 months he had a plan where he only paid $20 every three months. Now he's paying $25 every month with Top-Up cards, which is a huge rip-off considering he barely uses the phone.

I looked up the charges online and here's what I've found (under Account Activity), which I can't make any sense of:

Basic Rate 20˘ per min.
Top-Up by: 9/05/12
Minutes Left: 574 A/T Minutes - Expires 7/07/12
Current Balance: $7.18

Under Balance Info it mentions "Your Beyond Talk Plan"

So every month, before the Minute expiration date, my dad adds a $25 Top-Up. The last time he did this it seemed that it added 200 minutes and $25 to his balance. But then maybe 20 minutes later, $20 was subtracted from the balance for xtras. In May, $30 was subtracted for xtras after he topped-up before the minute expiration date.

Firstly, what in the heck are these xtras? My dad doesn't understand what they are and neither do I. He only uses voice, no texting or anything else (or so he says). I don't see any activity for anything other than Voice.

Secondly, how can he go back to paying $20 or so every three months?

Why are there two expiration dates (one for the minutes and one for the top-up)?

If he doesn't Top-up before the monthly minute expiration date, what would happen?