Xfinity has just horrible customer service

I have a plan with Xfinity mobile and got a "free" phone for adding an additional line.  I decided against the phone, deactivated the line, and returned the phone unopened to their warehouse via FedEx following all instructions provided.  Using the tracking number, FedEx confirmed that the package had been delivered, but Xfinity did not acknowledge receiving the phone.  I followed up weekly for two months, calling them, being put on hold, being bounced around from representative to representative.  Finally, two months later, I got a "confirmation"  via chat that the return had been processed.  Exhausted by the whole process, I took a screenshot of the chat resolution and put the whole thing out of mind.  A year later, it turns out that Xfinity has been billing me monthly for the unused phone.  I spent hours talking to customer service earlier this week trying to resolve the issue.   After talking with three different people, someone confirmed that my returned phone had been found and that I would be reimbursed.  Great.  I asked for an email confirming this resolution.  The representative said they couldn't provide an email at the moment, but that I would receive the email within a few hours.  Five days later, no email and the deactivated account and phone are still on my account.  I feel like I am being outright lied to.  Xfinity should be paying me for my time and effort pursuing this.