Position was not a good fit and wanted a position outside of collections.
"Not a good fit" is a bit too broad - that could literally mean any reason why someone would want to leave a job (so it's like saying "I left because I wanted to leave"). You'll need to explain why the position wasn't a good fit, or at least what would make another position a good fit.
I don't work in this domain, so I can't really comment on "a position outside of collections" - but it's worth thinking about (and being able to answer) why you specifically don't want to work in collections, and perhaps using this as the reason instead, or including that reason as part of saying you don't want to work in collections.
I did not like how the company treated their employees.
Some may see this as a fairly reasonable reason, as long as you can justify it when asked.
Although others may view saying bad things about a current / previous employer negatively.
So, a reason that focusses more on "different" (or "better for you") rather than "bad" would probably be best.
What is the actual behaviour of the company? If it includes lack of advancement and/or low salaries, you could consider something like:
I didn't feel like there's a lot of room to grow professionally.
There is, however, a fair amount of risk involved here as it coming across as you just wanting more money.
If the behaviour is mistreating employees, you could consider something like:
I had a personality clash with management.
This one may be a bit more difficult to justify honestly and without saying bad things about the company, and it may also make it come across like you're difficult to work with.