Reverse collections

Has anyone canceled tv service and returned equipment, but still had their account sent to a collection agency? 

Note, 3 Telus Representatives state my account was sent to collections because the equipment was not returned to Telus.  (Canada Post tracking number was sent late).  Canada Post tracking indicates equipment was received by Telus.  

Second Question:   Can companies reverse the sending of accounts to collection agencies?   I ask this, as this action by Telus may affect future credit applications, maybe for multiple years.  

Third Question:   anyone have any other email addresses for managers?   I fear Telus Representatives may not have the authority to reverse the sending of accounts to collection agencies.  

I am a loyal customer of Telus, about 29 years.   Thanks for input.