cancelled acccount. I'm still getting charged. DM's can't help. When I call the 1-800 number I'm told it's closed. What are my next steps?

Hello!

I hope someone on the forums can help. I cancelled my business account on 10/20/22. I've been charged every month since and am now told I have a past due balance. When I DM'd with customer service I was told they can't help me and I need to call the 800 number. But when I do that I'm told the offices are closed. 

What are my next steps?