Deleted internal storage trying to install T-Mobile lollipop rom.How to Fix.No boot.

Hi.I installed the T-Mobile Kit Kat rom and then tried to install the T-Mobile Lollipop rom and deleted my internal storage trying to install the T-Mobile Lollipop rom.Now phone want boot,but it does have twrp recovery installed and I want to know can I fix and return to AT&T stock Kit Kat?If so how.