Data bill R8000 phone locked How do I work

I have home WiFi. I am on the road all day working self employed. I recently 1 mtg ago upgrade to red advantage which gives me 2gigs data. Suddenly I get an sms which I thought was a hoax saying call urgently your bill is over R8k. WHAT. Seriously how the hell. Unacceptable how can you responsibly be managing accounts to allow this especially in this day of debt. I am seriously distressed. As a self employed person working on commission only my phone is now locked no calls no messages no whatsapp how do I run my business? I am losing money as I am unable to be In contact or follow up with clients. Totally u fair and you can only investigate at month end ??? WHAT. I want to cancel and go to another provider. This is the worst experience of my life. Dropped calls non stop. Now Data bill of R8k. And no one cares. I just get told I can only suggest you get another phone and aim and use for now. WHAT? Seriously.