so I didn't get settlement in writing.. now what??

Ok I know, this was really, really stupid. I trusted a collector for some unknown reason, and assumed that since he recorded the terms of the settlement he would adhere to our agreement. I even had him state in the recording that he would send me a settlement letter before the first payment was made. But he didn't, and I worked 5 12 hour shifts in a row and lost track of what was going on, and he ended up taking my first payment of $600 and putting it towards my full account balance at HSBC. And he sent a letter, but not a settlement letter, just a letter stating I was going to make 3 payments. And he set it up so that the letter would not arrive until it was too late for me to do anything about it. But long story short they are going to take 2 more payments from my account the next 2 months, and they also have my bank information. So they can clear out my account, I'm assuming?? What's my best move at this point? Any advice? Do I need to get a new bank account now? btw this was with United Recovery, scumbags of the earth..