Complaint sub-issue: Right to dispute notice not received

After some 20 years of service with XXXX I found out that I was paying for XXXX recorders even though XXXX had a " new '' recorder that could do the same with only XXXX recorder. I was upset and checked my account and realized I was paying about {$250.00} per month for service I did not use. I canceled XXXX XXXX and switched to XXXX. My bill dropped to less than {$75.00}. 
XXXX sent me instructions for returning the equipment. t turns out that most of the equipment was worthless, but they wanted XXXX pieces to be returned to them. About three weeks later I received instructions to pack the XXXX pieces of equipment in the boxes that would be delivered to me. The rest could be brought to XXXX for disposal. However, the serial numbers for the XXXX pieces of equipment did not match any of the XXXX pieces I had. I called XXXX and eventually the agent I spoke with gave me the XXXX serial numbers of the equipment I wanted. In the meantime XXXX box arrived with XXXX sections and I was told to put the XXXX pieces in the box and take both the XXXX pieces and the rest to XXXX and they would dispose of the old unwanted equipment and bring the boxed equipment to XXXX XXXX. About one month later a received a letter telling me I had never returned the equipment and that I owed them {$230.00} for the equipment. I called them and explained what had happened and they disputed that they had ever told me to take any thing to XXXX. I told them to check all the recorded phone calls to me that they said were being recorded and if I was lying I would pay the bill and if not they would have to write it off. After a few more bills telling me I owed the money I received a letter from AFNI, a debt collector. I called them and explained what happened and they said they knew nothing about the debt only that they were empowered to collect it. If I did not pay they would file a complaint. I have no idea what they filed but during this time I was surprised that I was unable to get a loan to pay for an XXXX that I had ordered. I thought it might be my age ( I am XXXX years old ) but I had a great XXXX score ( XXXX ) and the financial ability to pay for the XXXX myself. 
Last week I received a call and a letter from AFNI offering me a 25 % discount off the current balance and telling me that my this had been reported to the XXXX credit agencies. I went on line to my XXXX to check my XXXX credit score and I was stunned to find out that my rating had been dropped from XXXX to XXXX two months ago. No one had contacted me from the agencies to notify until after I contacted the Afni. 
Given this action, I immediately called and paid the bill under duress because it was not a debt but a dispute. XXXX XXXX filed it as an unpaid bill. For over 20 years, every bill I ever received from XXXX was paid on time and in full, automatically, as are most of monthly bills I have that do n't vary from month to month. None of this history counted in my credit report. All this for a dispute. And now, to rub it in my face Afni the debt collector told me to call XXXX direct to speak to a supervisor about adjusting my rating back to where it was at XXXX. Another call was transferred to a random phone number. 
I am a retired XXXX with the resources to fire back at them but I do n't want to waste my family 's inheritance. So I want to file a complaint and hopefully amend the law to distinguish between a debt and a dispute. Especially when a person 's credit rating indicates no unpaid debts in their credit history.