What is a "good will" credit on my sprint bill?

i just recieved my sprint bill...i've not used it in like...almost a year now....but havent had the money to pay the 400 cancelation fee's....i got it today and shows that i was credited....basically all the charges so far this year...are gone...so whats a good will credit?

or is that sprints way of saying pay us so we cancel your account we are tired of you???
lol believe me...no complaints here....

i just wanted to know what it meant