Unexplained data charges of spending limits on contract SIM cards

I’m writing this with my heartbroken MTN is a **** they charge you for thing you did not sign up for. I took a contract in August and I’m regretting daily because I was not told anything about spending limit suddenly I’m now owing MTN 10k they even closed their SIM card on the 2nd of November until I pay for spending limit I even sent them emails of my banking account to show them I’ve been buying data since day 1 I received the SIM card, I was told no stories I need to pay up and if I don’t the money is raising I don’t know what to do because I am heartbroken I owe R10 000 to spending limit that I don’t even know apparently it’s the data that runs through background apps that data costs 5k I regret taking their contract