Don't understand a cancellation

I have had allot of problems with Cool Ideas, there was always a internet problem on a Saterday and Sunday during the times when support was not in the office. So on the 1st of January 2024 I made a payment to Cool Ideas, on the 4th of January 2024 I phoned Cool Ideas and asked the agent if the payment made on the 1st was for the month on January on which he confirmed "yes" so I told him I want to cancel how do I go about it. He said I must give one month notice and tramsfered me to the cancelation department. The lady told me I must send an email stating that I am cancelling which I did on the 4th of January 2024 stating that my last day with Cool Ideas will be on the last day of the month, that would be January 2024. On the 1st of Feb I got an invoice from them, then today I got an email from Cool Ideas saying I am 5 days behind on payment, and an sms today saying I am 6 days behind. Dont they understand a cancellation