No we are not convinced that they are right, as I've stated, in previous post via the Pantip link, that many people are claimed to be wrongfully charged, so we are not alone in this. And they could've asked us to pay via usual means via True Call Center or Terminating current service under her name, since She is still a customer until today.
If at the end of the day they have anything right, It's also my right to terminate accounts for no reasons if I choose to, but in this case I will tell you that it is based on that it's a TERRIBLE Customer Service (if it's their deed to settle the unpaid amounts via Debt Collector rather than other means.. after 6 years of us not knowing/ being informed via usual means like most other services from other companies).