cant cancel my plan

I'm be been trying for weeks to cancel my plan. 
 

I get error messages every time I go through the portal, and even when I try to change my plan, I get an error message to say it hasn't worked. 
 

I've now been charged over $200 and no replies to any emails, with the 'talk to real people' cheat option cleary being a bot, which just sends me back to the cancellation page which doesn't work. 
 

I'm at my wits end with this and out of ideas short of starting legal action.