Cancelling incorrect invoice and insurance

Middle of January 2021 i noticed that my insurances at Zilveren Kruis were not canceled correctly. After calling the agent confirmed to me that my basic insurance and additional dental insurance is canceled and all fees will be waived. That sounded right.

After a month I received an email that I am late with my payments. Also I was still charged for the dental insurance on February. 

I called once again, this time there was a different agent which confirmed to me, that the first agent misunderstood and only made sure my basic insurance is canceled, and that she will now cancel the dental insurance and waive any costs that I still need to pay and refund what I had paid, because it was supposed to be canceled.

Now, week later, I received 2nd reminder to pay my bills.

Sorry, but this is ridiculous. My only way to communicate with you is through phone and then 2x the promise is not completed. I risk my file being send to the Incasso services and having a record there because of incompetence of Customer Service agents.

Anyone else has been in this situation? And ZK please get to your senses and cancel the insurances for good with my money back for the year!