Lost phone by ATT's 3rd party Logistic and ATT is charging me

So I just got off the phone with this department

Can someone explain to me how I shipped a phone back to ATT for an upgrade, it shows shipped out on the USPS site they show it received it at the 3rd party Logistics, the 3rd party can't find it and ATT is charging me.

They are also telling me if their 3rd party can't find it I get charged because they never saw the phone even though their 3rd party shows they got it.

So I did everything right

I sent the phone back

It was received by their third party

As of know they can't find it 

So they want to charge me because they can't find the phone.  

This is almost a consumer fraud issue where they "suddenly" loose the phone and charge back the customer for a phone their 3rd party lost. 

So they get the phone and my money definitely a consumer issue that ATT should know better

Off to consumer advocacy and Arbitration as this seems like a massive set up to get more money from the consumer.

The right thing is to rebate my money and charge back their 3rd party not me.

Disgusting way to do business as it breaks the trust of the return phone.  I as a consumer have to worry if they loose something I have to pay for it.

Am I missing something??