Swift Funds Agressive collection techniques, illegal practices. Las Vegas NV

I was a member at a gym in my city. Myself and my boyfriend who both signed up at the same time went to the gym one time and decided it wasnt a good fit for us. We cancelled our services and ended up not returning, all of our fees were waived and everything was taken care off. 4 months later I recieve a call from a " John Banks" from Swift Funds. He advised me he was a debt collector for the gym I attended and that I had 2 days to pay 300 dollars or it will be flagged on my credit for 7 years. He never read the mini miranda and proceeded to threaten me. I advised Mr.Banks that I was more than willining to work this out but I will need to speak to the gym becuase I believed the amount was incorrect because I had only been to the gym one time. He told me "You can call them but you are wasting your time becuase they will direct you back to me and that is pointless because you will not be able to get the amount reduced," I said okay whatever I can pay but I dont have 300 dollars today. I will have to break it up intp a couple payments. He said " If you dont want this flagged on your credit you have to make a mininum payment today. They he proceeded to change the amount that was due, and he did this three times throughout the call. I asked him if he could give me this all in writing or via email " He said you dont need it in writing if you dont want to work this out, fine it will go on your credit." I told him that I never said I didnt want to work this out and that I wanted to have this all in writing for my records. He proceeded to decline that and basically called me an idiot. I also asked him, do you have a website I can pay on I dont feel comfortable giving you my account information over the phone espcially since when I call you answer the phone "Hello" not "Thank you for calling swift funds". He said we dont have a website. Which was a lie. So after 10-15 minutes of arguing with this dude I tell him I want to be reassigned to someone else. He laughed and said no Im the manager. I said okay and hung up the phone. I ended up having a voicemail from a lady that worked there as well and called her and went over the whole situation and she advised me that he wasnt a manager and that she "hated" that guy. When speaking on the phone with this girl who was not very intelligent and cursed on the phone to herself multiple times in conversation I decided I was just going to work with the gym. I called my local gym and spoke to the manager and explained everything. After about two days of getting everything figured out we came to settlement and I ended up paying 100 and we called it a day. I can tell you I would love to give "John Banks" a piece of my mind..... Jerk.