Santander Consumer Usa Formerly Citi Financial Auto Loan changed without my knowledge. Verified my address 5-6 times, still nothing in the mail. Started to get scared so looked up complaints online and I need your help! Internet

Santander Consumer took over my automobile loan from CitiFinancial. I was never notified via mail phone, email - nothing. I never got a bill so I had no idea what was going on. Then the harrasing phone calls started. I didn't know where to make my payments!! I started to get scared that it could really hurt my credit so I called them back. The "customer service" reps are so incredibly rude. I said I don't know who you are I am scared to make a payment to you. Here was the response that I got "Well MA'AM you have been making your payments why would you say that!?!"
I told the rep that I wanted to make my payment so that it won't hurt my credit.
Then I started researching this so called company and I came across all these reports. and I decided that I need to file this complaint and let everyone know my experience.
Well today I called and made a payment for $1000. Since it was a large payment I did not want to use the automated system and I don't think its too much to ask to have a receipt faxed to me. Well I finally got through to them after 4 attempts and being hung up on 3x. The rep said "MA'AM we don't fax receipts to people" She said she could email it if they had an email address on file. I told her my email. Spelled it slowly and phonetically. Its been 3 hours, and no receipt has been emailed to me. The was $1000! It was my yearly bonus from work. I am so scared that they are going to screw me over and not give me my title when I pay it off.
I have a mere $1700 to pay my car off. PLEASE HELP ME!!!