Bill came already

I saw an envelope in the mail yesterday from the hospital, and I incorrectly assumed it was about our refund from the IVF. Nope it was a bill for $2,250 for the IVF. Unbelievable. I just can't believe that although they have had our $8,200 since June and the IVF was totally done on August 7 (day our blast was frozen), they still have NOT processed our refund yet (of I figure $1K) yet they have already sent us a bill for the FET which won't start for about another month. Well I am hoping we get our $1K back before I have to pay this $2,250. I plan to wait until the last minute (right around Oct 1) to pay it.