Unable to return the xfinity mobile

Having problem with returning xfinity free phone given as a compensation. Had calls with multiple customer service agents / supervisors / store people but not able to solve the problem. I am here to sincerely request the help to return the phone. The below is all about the case. 

• I had a problem with my internet and tried to resolve it with customer service. 
• They accepted the problem and gave me a free samsung phone as compensation and they said the phone and line is free for one year and can be cancelled and returned anytime.
• I asked them to cancel the line and how to return the phone back later. Over-call customer service cal, they canceled the phone line and told me that they will send a return label but I didn't get any return label.
• So I called them back and asked for a return label. This time customer service said that the return label will be sent to my mail and gave me the reference number - ecm0018055695.
• Since I didn't get any return label I called them again for the same and today they said they can't do it over customer service and directed me to the local store. 
• I went to a local store here in Manteca and the store manager said he couldn't take the phone in the store and routed me to the corporate store in Tracy. 
• I came to Tracy corporate store and the staff there said they can't help and Assist. manager gave me the CSA department number. 
• When I called CSA, they talked to me andAssist. manager and said that they can't help on it.