Extremely unreasonable data usage

I have been very disappointed with Vodacom service. After having a data contract with my ipad for 10 months, my account got suspended for no known reason. When I phoned to enquire they said they didn't know why it had been so they unblocked it. Just days later this happened again. When I phone for the second time they eventually concluded that it was because I had reached a cap of the amount of data used. I had never before this time EVER used over my purchased amount of data (1GB). This was followed by 2 months of being billed over 3 times my usual amount of R389. Not once was I notified about this totally unusual data usage during the month. I was not notified after the first month of high data usage until my account was blocked half way through the second month. I was not even given the chance to see what had been causing th is very strange high data usage to stop it from happening. There are some days where it is recorded that I used over 1Gb in one day, on days when I was home connected to WiFi. Now they offered me a 40% off the two bills but have failed to even follow through with that. I don't believe I should even pay the extra amount for the second month!