Ridiculous Data Bill

So I am a 53 year old woman using my mobile phone for items like Facebook, what's app and mail. I have had a contract with cell c for almost 10 years now maybe even longer and never have I had such a huge data bill!! I have been trying since November to find a solution with Cell C as to why my bill is so much?? I have been told that I changed my data limit to R2000??? Are you kidding me!!! I can't afford that amount so I don't know where they got it from when I asked at the cell c Gateway branch for assistance the answer simply was you used the data you should pay for it. My account has in the mean time been suspended as I refuse to pay such a ridiculous amount until I know how this has happened.. Feeling so frustrated!!!