Credit for turning in phone DENIED

Moving over to Xfinity has been an absolute nightmare!  We mailed our two old phones to Xfinity for credit and USPS lost them both.  Filed a claim with USPS and went to the store and they put in a ticket for us showing we had mailed them and asking them to just apply the credits for us, it wasn't our fault and I have the paper trail to show everything.  Xfinity rejected our claim.  Miraculously USPS found our phones and rerouted them to Xfinity.  Of course, we were now past the cutoff date, so they rejected our phones again and sent them back to us.  My husbands was rejected due to it being past the cutoff date and mine was rejected saying wrong phone was sent.  I did my own research to try and figure out how they came up with that and the employe at Xfinity put the IMEI2 on the form and not the IMEI.  If you clearly look at the phone and go into settings or look at the Apple iphone box I mailed them in you can see it was the correct phone as BOTH IMEI/IMEI2 are listed.  I went back to the store, and they filed another claim with all of this info, and the claim was rejected again!!  How can you fault me the customer when I did exactly what I was supposed to and it was not my fault the employe put the wrong IMEI on the form even though technically it wasn't wrong as it is on the phone.  I went back to the store again (I should just get a job there at this point since I'm constantly there) and they tell me there is nothing they can do and to just sell the phone myself.  Why exactly should I have to do that when Xfinity is making money off me for 3 phone plans monthly.  I don't have the time for all of this back and forth or to try and sell my phone.  I want this corrected now.  There are plenty of other cell phone companies that are more than happy to pay off my cell phones to gain my business.