Question about change fee
 

If the fare difference is lower do i get money back when i change a ticket?

never experienced any airline giving back the fare difference if it is lower. Others may have a different experience though. The only way to get money back so to speak is if ticket is flexible, cancelling and re-booking.

It depends on fare flexibility rules. Generally speaking, yes: if change is allowed by original fare rules, it results in either a charge or refund of fare difference.

That is, minus a change fee defined by fare rules, and minus whichever phone/administration/handling/agent/ticketing fee airlines come up with.