Home-connect's cancellation "policy"

I have been with Home-connect for a few years now. I just saw that I had a positive review last year but unfortunately, this is a complaint. I have found a better service provider and requested a cancellation. Due to my requesting a downgrade in service, I was not able to log the cancellation on the app. I called the call center before 1 March 2023 and explained and I was told that someone would contact me to help me cancel. I then received my March invoice via email and decided to respond to that email also telling them that I want to cancel, they are more concerned about why I want to cancel. I was again told someone would contact me. On 1 March I decided to log the cancellation on the app after I never received a callback. I have now received an Invoice for April. This is what they wanted, they made sure I wasn't able to cancel in time so that I have to pay for another month. I have sent a complaint and was told I am still liable for the April Invoice. No effort was made to go and check the calls or emails, I am expected to do their jobs for them. This is absolutely ridiculous.