Supersonic service is poor

I cancelled my contract on 30 Nov 2023 for 31 Dec 2023 by email. Supersonic acknowledged receipt. End Jan 2024 I once again received and invoice. I was on their chat line for close to an hour before I hung up. Same thing end Feb 2044. I have just received the April Invoice. They owe me a refund for 5 months. I was on their chat this morning - and hung up. I tried their telephone number - and hung. The worst service you can imagine.