Is there a way to send in a formal complaint?

What happened was I went to purchase a new iPhone at the Xfinity store and the rep misled me and claimed she couldn't process a trade in, so I bought the phone and it needed to be shipped to me.  When I discovered that she was incorrect (not sure if she just didn't know or didn't want to bother) I tried to process a trade in but was told I couldn't, so I just tried to cancel the order but it was too late.  I was told that when it arrived, I could just return it.  So I went to Apple and bought my own iPhone, did the trade, and transferred everything.  

When the phone arrived, I called Xfinity to get a return processed.  They claimed that they needed to "activate" the phone in order to process a return (remember, this phone is still fully sealed in its packaging) but they somehow ended up disabling my current phone.  After an excruciating 2 1/2 hours, my phone service was resolved and I got a return label, so I sent it back.

A couple of days later, Fedex confirmed delivery and I got a "We've Received Your Return" e-mail.  All good.  Except that two days later, I got a "We Haven't Received Your Return Yet" e-mail.  So I called again and was told that multiple orders had somehow been generated and they didn't know where anything was.  So I called again and was told that the other orders were actually system generated and there were no problems and that everything was processing.

Weeks go by and no refund.  I called AGAIN and was told that there was an open order that needed to be closed and that there was a transfer that was pending.  After an hour, the phone rep suggested I just go into the Xfinity store.  I did, and the rep there was horrified at everything and could not understand what was going on, got in contact with technical support and they were going to push the refund through.

However, a couple of hours later I see that my phone is disabled (only "SOS" and not service) and so I go back into the Xfinity store and this time, they couldn't resolve anything so I went home and got on the phone with support and another 2 1/2 hours later they were finally able to resolve and get my service back.

Sorry to be long winded, but wanted to make sure you understand what brought me to this level of frustration.