MAX AMOUNT ON CELL CONTRACT

I went into Cell C and entered into a new contract for my son on his old cell number. The lady asked me if I want to make the account to not go over a maximum amount of R50.00 and I said YES. I was told that the account would not be higher than R450.00. I receive the account today and it was a total of R520.00. Upon my query over lunch time at the CellC Shop at Heiderand I was told didn't they tell me to come back the next day so that they can activate the R50.00. THEY DID NOT. All the lady could say now is \she is sorry". If I settled for something and even signed for it and this kind of service occur it will make me think twice to get another contract from CellC. In my books R70.00 may not be much but for my son it is a lot of money. The people at CellC is very friendly I must say but if you promise something a customer should not have to go back because the outcome is different."""