Product: Debt collection

I submitted XXXX year ago a complaint ( I can not find link to login to my reports account on CFPB ), but you can review it on my account.It was about XXXX Card, account. We had a miscommunication in XXXX with XXXX XXXX Bank credit card, and I missed payment, they filed with credit agencies. The XXXX Bank reported me to XXXX Credit Report Agencies. At the time I was unable to pay for this debt, but now I can. 
I subscribed again to XXXX XXXX ID protect what gives to me XXXX credit reports in once, with scores. 
And I see that in XXXX BANK has a negative account for me. collection account they said, and it is {$990.00} But they sold my account to another company, MIDLAND CREDIT MANAGEMENT INc. and now this company filed negative account just the same as XXXX BANK did. 
But It is illegal ; if XXXX BANK sold my account to MIDLAND CREDIT Mngt the secondary company can not report me to the credit bureaus anymore. 

The reason I know about it is because in XXXX I filed XXXX to stop foreclosure. In XXXX there were credit cards including XXXX card. which later sold this debt to a company in XXXX and XXXX in XXXX did not post this BAD debt ( Bought as bad debt from XXXX in XXXX ) on my credit reports. 
Is it legal, that the company who purchased Bad Debt, will post it as BAD CREDIT for me? Because After Midland Credit Mngt co mailed to me a letter about to collect {$990.00} XXXX from me. for the debt to XXXX BANK XXXX ( XXXX ) XXXX, I paid it off on XXXX XXXX XXXX. The Midland Credit mngt said that they mailed to me PAID OFF letter. 
I do n't have " PAID-OFF '' letter from MCM yet, but I have a text message from XXXX bank about PAID OFF to Midland Credit Management, INC.. 

My question is : XXXX BANK XXXX ( XXXX ) XXXX sold my bad not collected by XXXX BANK XXXX ( XXXX ) XXXX debt for profit to MCM. 

XXXX BANK XXXX ( XXXX ) XXXX posted negative information on my credit reports. 

After MCM assumed ownership of bad debt account, they also posted derogatory information on my credit reports. 

Are they allowed to buy bad credit with intent to post another derogatory information about me? because once MCM BOUGHT it from the XXXX ( XXXX ) XXXX, the XXXX ( XXXX ) XXXX got paid for my bad debt. 
And now MCM got paid too but it is only XXXX company who is allowed to post negative information not XXXX and MCM got paid by me immediately. 
What can I do?? Is it legal what they are doing? 
I called to MCM today and asked why they posted negative information about me on Credit Reports? Because they send me a letter, they threatened me with lawyers and courts and legal action, I called them back and paid in full right away- and yet they posted negative information about me anyway. 
The XXXX ( XXXX ) XXXX is not XXXX company they are from XXXX but do business in California and Nevada. 
the MCM belongs ( I was told today ) to ENCORE CAPITAL, wich is listed on XXXX I was told to day. But when I calledto XXXX number, for MCM in XXXX XXXX -it is forwarded to XXXX . 
People who answer are XXXX or XXXX but they are XXXX citizen and in XXXX so they use XXXX names for comfort to customers. I asked today if they are in XXXX? " XXXX XXXX '' he said his name was, laughed at me, and said no, not in XXXX but in XXXX. 
I asked him : why did they report this account as negative? because they received paid off. 
He said because they bought it fr XXXX ( XXXX ) XXXX as Bad DEBT, they can list it as BAD DEBT. 
I asked him : does he know if it is legal? 
he said, that MCM is part of ENCORE CAPITAL. they listed on XXXX, and hung up. 
please advice me what can I do? 
Maybe I must hire LAWYERS to help me to fight this? please advice.