Netstar need to get their finances in order!

I've recently been contacted by someone from Netstar saying an amount was outstanding for one car that was sold 6 years ago, and the other sold 6 months ago. I was convinced it was a **** as I was never able to get through to the individual on the number listed. My husband went and paid the amount allegedly outstanding, and was sent an email to say the account was now closed. A week later I receive an sms saying the money tad been deducted from my account. I'd like to understand how Netstar can pop up with an amount owing from 6 years ago which I had never previously heard of, and now have managed to be paid twice on something I still don't believe is owing, but was happy to pay as I simply don't have the time to figure out what they are doing. Very unprofessional behavior.