Has anyone had an Issue with an Insurance Claim

Has anyone had an issue with an insurance claim? I filed a claim for an iPhone6 plus, they sent me a new phone and charged my credit card. I realized that after all was said an done, my phone was not broken and decided to return the new phone sent. Used return material they provided, sent via USMail as suggested, have proof we dropped off and still no credit to my card. Contacted the insurance company to be told that it may take a while to receive and call back in 20 days. Marked my calendar and contacted them to be told that they still have not received my return. I have filed a claim against my first claim to be told that often times there is an 3rd party outside carrier used and they don’t scan the packages picked up by them for delivery. Basically I’ve paid for a phone I don’t have to be told oh well. Nothing we can do on our end. What proof do I have that they actually didn’t receive it? I have proof I dropped it off. I’m extremely disappointed in the insurance company and ATT states it’s not their issue, because they are using an outside party. 

Has as anyone else encountered this problem? Any information you could share would be appreciated.