Telecom USA Billed me for calls made 5 months after number disconnected. Calls were from Nevada. Jacksonville Florida

We moved from the location that had the phone number relating to the charges in February 2014.  The calls were from Reno, NV on 7-27-14 and Las Vegas, NV on 7-27-2014.  We disconnected the number in previous residence in February 2014 at time of move.  Have made numerous calls to Telecom USA's customer service number 800-226-0014 and always directed to leave a detailed message, that no one is available and that they would promptly return my call.  They never call back.  The two calls they say I owe them for total 29 min. and the charge is 86.57.  I did not make or receive either one of the two calls in questions and was not the owner of the phone number they were charged to.