Bad, bad ,bad service Netstar

I signed a 3year contract with Netstar 3 Jan 2019. 17 October 2021 I emailed and canceled the contract with notice. Cas-***-c4x5. No one got back to me. 21 Dec 2021 received email over debit order change. According to me, Dec 2021 was my last installment. I called them. Cas ***-x8f5. Debit order went 3 Jan 2021; I reversed it. The 6 Jan 2022 send an email. No reply. 15 Jan 2022 send another email asking them to get back to me. 18 Jan 2022, got a reply explaining that 3/1/2022 was my last installment; which I paid immediately and emailed them proof of payment. Since then I am getting calls and sms-es from debt collector...my account hasn't even been outstanding for 15days. As a good paying client been treated like that....Netstar has lost me