Why is Sprint charging my deactivated account?

I have moved to Canada where Sprint is not available, and switched carriers ages ago.

I don't have the SIM card or really any of the security crap they would like me to have when I call them.

I finally had the right to deactivate my account in "my sprint" after Tmobile acquired them. At the time I paid off the $60 bill remaining on my account and assumed i was done with them.

Today my parents found a letter from a collector looking for $130. I check my account and sure enough they have been billing me since October, and up to May when my USA bank account was finally closed.

 An someone please tell me what I'm missing here? Why have I been getting charged for months on a dead account?