Netstar traker

I have canceled my services with Netstar in Desember because they deduct more money from my account without any explanation I decided to phone them, Luckily I took the person's name and reference number for the phone call, I phoned them after they just simply ignore the emails I have send them without any reply I got frustrated and phoned them.

But every month since then they keep on to deduct money from my account. I cancelled the debit order from my bank account but they still find a way to deduct money.

Iam very unhappy and don't know how to stop them from taking money from my account.