Data notloaded on contract resulting in a high acc

a few weeks ago I requested that once of data be uploaded on my contract, I am shocked today to receive an email that I am over with R526. When I call I was advised that there was an error when they were uploading my data. Now my question is who is supposed to pay that money where the error lies with them, for failing to advise me that the data was not uploaded. I then requested again this morning for data to be loaded, it is still not loaded. I spend money call Altech because their agents say they cant call me back. I feel it is unfair to be treated like this where as this is my second contract with altech. for the past 2 months I have been paying very high amounts on my monthly bill , I cannot afford to pay this much because I am sinking in debt because of a cellphone contract.