Closed sub account sent to collections

My Verizon account had a sub account for my ex husband.  When he went to get a new phone in Oct 2021, his sub account had a past due balance of about 58.00.  He had to pay this past due amt in order to get a new phone.  The sub account was then closed, and he was given a new account in his name only.  Now the 58.00 is still showing as delinquent, and has been reported as a derogatory status on MY credit report, because I was the primary acct holder.

I went to Verizon for a new phone prior to this, in July of 2020.  This same past due amt of 58.00 also showed at that time, which I paid in order to be able to purchase a new phone.  So this amount has been paid twice.

I have contacted the recovery dept of Verizon multiple times, talked to the collection agency and no one is able to help with this issue.  

I have been a customer since 2016 with perfect payment history. I have spent the last three days trying to resolve this, and every representative I speak to seems to favor losing a customer over helping me to get this removed from my credit report.

I am disturbed and appalled at the run around I've been given, the misleading tactics of lower tier customer service, and the unwillingness to address my issue.

If not resolved in the next couple of days, I will file a complaint with the BBB.