Walmart Family Mobile Sent to collections - Unexplained Nationwide

I canceled my daughters Walmart Family Mobile account in December 2014. It is now November 2015 and I have received a collections notice from Receivables Performance Management stating that I owe Family Mobile $106.45. I have attempted to contact Family Mobile directly but that is virtually impossible if you do not have an active accout with them. I decided to call T-Mobile and a rep was able to get me on the phone with a Family Mobile billing rep who was able to locate my account via the account number referenced on the collections notice but would not provide my any information because I couldn't remember the phone number or pin number from the old account. The Family Mobile rep did state that when canceling an account there would still be a one month bill owed. If that is the case I should only owe $35.00 as that is what I paid monthly for this NO CONTRACT phone, where are they getting $106.45? I also advised the Family Mobile rep that I never received a bill or notice for money owed and that I have lived at the same address for three years, therefore if a bill were mailed to me, I would have received it. If I truly owe this money I will pay it but I want proof of the bills that were supposedly sent to me along with an explanation of the amount they are stating I owe.