Product: Credit card or prepaid card

my issue is with an item I bought from Amazon, on their Amazon Prime Store Card, issued by Synchrony Bank, returned to Amazon, Amazon acknowledges the return and has stated they have issue multiple credits, multiple times for this ONLY item on this card, and yet for nearly 1 year now, Synchrony Bank has posted NO CREDITS. 
Today XX/XX/XXXX I get an email from XXXX XXXX stating my credit report now shows a delinquent account, and an email from XXXX stating basically the same. 
So NOW my credit score has been affected, and I have never missed a payment in my XXXX years of living. 

XX/XX/XXXX - ordered commercial XXXX XXXX from Amazon ( order # XXXX ), needed this immediately for my small business, item shows as ordered, I never receive it. * My Amazon analytics page shows Return Reason as SHIPPING ADDRESS UNDELIVERABLE for this item and order. 
XX/XX/XXXX - I call Amazon, explain the situation that I did not receive this blender, and I urgently needed it, so Amazon says the item is LOST. Reorders another immersion blender for me, this order number I believe is XXXX? 
I waited a few more wks, no immersion blender shows up from Amazon, period! 

XX/XX/XXXX - I ordered the same immersion blender from XXXX, and I have the order confirmation, and it was delivered a few days later. 
I've had the charge posted to my Synchrony Amazon Card account, I've had to dispute the charge with Synchrony Bank, back and forth, back and forth, resolved, then not resolved, etc. 
XX/XX/XXXX after a call with Amazon- spoke with Amazon just to make sure they issued 2 credits since I never received either immersion blender. I called them a few mins ago. 
XXXX from XXXX said there were 2 credits/chargebacks issued for the 2 immersion blenders I never received, and she provided me with the chargeback id # issued to Synchrony Bank XXXX They are as follows # XXXX {$620.00} on XX/XX/XXXX, and # XXXX {$620.00} on XX/XX/XXXX. This should bring my account up to date with both credits. 

** XXXX XXXX XXXX - randomly I receive from XXXX a extremely dirty box, like its been laying around collecting dust, etc. with the IMMERSION BLENDER I ordered from XXXX back in XXXX. Just out of the clear blue sky, XXXX tracking number was XXXX, and Amazon did and will confirm that this was returned and received back to Amazon. The only Immersion blender I have is from bakedeco.com, paid for using my person credit card, has nothing to do with Synchrony. 

XX/XX/XXXX - Email from Amazon showing me the 5 times they have issued credits to my Synchrony Amazon Store credit card account, and still nothing shows on the Synchrony statement, no credits exist and I continue to receive account past due, phone calls continually, etc. This entire time, I continue contacting both Amazon and Synchrony, because Synchrony ALWAYS tells me that I have to contact Amazon, they have NEVER RECEIVED ANY CREDITS from Amazon, and this just continually continues. By XX/XX/XXXX, I've called Amazon at least 18 times, and Synchrony Bank regarding my account minimally 15+ times with no resolution, still to this day.

NOTE : I was told by Synchrony IF a credit was issued, and the item in question was under dispute, that credit would NEVER post. What? Makes absolutely no sense.

I've tried unsuccessfully to escalate this on both sides, no luck at all. 
XX/XX/XXXX - lastly yet another call to Amazon and XXXX sent me an email showing me all of the additional credits they posted on XX/XX/XXXX and says it should take up to a week to post to the Amazon Synchrony Store Card. 
XX/XX/XXXX ( I think ) was the 2nd time I've called and even logged in to my Synchrony Amazon Store credit card account and there are STILL NO CREDITS POSTED. 

I have rarely used this Amazon XXXX XXXX XXXX from Synchrony Bank, period. If you check the purchase history on this card, you will see only a few charges all the yrs I've had this card. Now that they continue to escalate something that should have been handled nearly 1 year ago and my credit is now affected, I am closing this account once my credit is applied and account history is cleared. 
Please know at NO TIME was anyone from Synchrony Bank interested in researching or doing anything at all. Every voice message stated to call their number, every time I did they wanted payment, and I continually told them what was going on and honestly they could not have cared less. I've read a lot of complaints only yesterday about Synchrony bank suing customers and lawsuits, etc. 

the tracking label for the randomly received XXXX blender I received in mid XXXX, is attached as well. I have tons of other documents, I can send over it needed. Additionally I have the documents I received yesterday after Synchrony Bank filed with the credit bureau regarding my account with them being delinquent. Whatever else you need I can certainly send over. I didn't know I needed to attached the documents, or I would have better organized them. Thank you so much! Sincerely