T-Mobile non return fee on gareway scam

Got me today as well.  Canceled our account paid our full amount off so they would release our phone numbers as we moved to xfinity for ½the price.  They said they would send me a return label and never did. Called asked for another said they did but we never received it forgot all about it then seen a $250 charge on the account so we called they said we needed to return our device and they would return the money. Returned it still have the receipt but now they are saying they won't return the money since it's a " service fee " and not a payment for the device it's self.  So we are going to make a claim with our bank showing it was returned and see if they will return the money