Collection agency hiding its identity

For the past few months I have been behind in my credit card bills. My boyfriend was out of work and its just hard to get back on track. Last week we signed up for a dmp program and wwe were so excited to start paying our debt back. The next I got a call from a guy stating that he was an attorney and my Best Buy card had to be paid in full or else I was going to get sued. Obviously I was scared and don't want to get sued so I set out to do some research on practices on collecting debts. While i have been kind of avoiding there phone calls because I didn't want to say anything that was going to screw over more then I was. Last night I stumbled upon the Fair Debt Collection Act and it states that the attorney has 5 days to send you paperwork stating how much you owe and so on. I found that on day 7 after the first phone call. I started to think dont' lawyers know the law and abide by it so where are the papers. This morning I called the Best Buy credit services and asked whom is my debt being collected by and she told me Corporate Receivalble!! not even a lawyer at all. I told her about the attorney calling me and she said it was probally just scare tactics. Isn't that illegal to impersonate a lawyer!!! I have money to pay part of my balance but dont wasn todeal with Corporate Receivable what should I do???