Cancellation and invoices

Hi all, I've tried emailing Zoom and tried the chat function but can't get assistance with the following:

I cancelled my Zoom subscription. When I was it offered me a discount but wouldn't allow me to avail of that, so I would like to cancel completely. I completed the process but I continue to receive invoices. I haven't paid these as I've cancelled and am not using the service. How can I clear this up since email and chat goes unreplied to? 

Preferance isn't to have to sit on hold either for ages.