<human>: Condense the text into a few key points

NY - Holy shit, my online bank sent out money to a cancelled bill payee because they converted their website, and when they did the conversion, it inadvertently reactivated cancelled bill payees. What can I do? This is a huge chunk of money (rent in a large city). 

This is Ally Bank by the way. We use bill pay every month for rent, and because we were moving, we cancelled our old landlord as a payee and cancelled any future payments in late October. However, they sent out a check on November 27th to our old landlord, and obviously, he cashed the check. We saw that this huge payment came out today to our old landlord via a bill pay check, and called Ally because we couldn't find the landlord as a payee and had no idea what was going on. What we learned on the phone was that when Ally converted their website to the new system, it activated old and cancelled payees for some accounts!! So Ally sent this payment out without our knowledge or authorization, it was essentially a "blip" in the new system. 

Ally admits this is their mistake, but they asked us to get the money back from our landlord and won't provide us with our money! Like we are ever going to see that money from our landlord, he doesn't care, the check is cashed. They used our money to send out an unauthorized payment and won't refund it! They admit that this was their mistake!! WTF. 

What can we do legally? Fortunately, we're not paycheck to paycheck, but I'm sure others are and this is so shitty! It's their fault 100%. What do we do?
<bot>: Ally converted their website to a new system and it inadvertently activated old bill pay accounts. They sent out a significant unauthorized payment to our old landlord and then told us we had to get the money back! What do we do?