Deposit NOT refunded by Xfinity stating my deposit was used as credit/adjustments for my billing????

I disconnected Xfinity and now they are saying I don't get my deposit back because it was adjusted or credited (Xfinity didn't even know which one) into my 1st and 2nd months Bill's (DEC 2017!!!). Which is not correct. I have copies and none of my bills have credits or adjustments!?!? None the less he said no, "you will NOT get your deposit back? Has ANYONE gone through this craziness???

So now I get no return🤯