Over charged for Neotel Broadband LTE

Dear Neotel Team<br> <br> I have a Broadband LTE 15 GB account with you where I am supposed to get 15 GB of data every month. Every month somehow I see that I exceed the 15 GB mark and get billed anything between 1200 to 1600 rands per month. I cannot afford to pay so much for internet every month. I have placed multiple calls to the call centre to put a cap to the account at 15GB so I do not exceed the limit but it has not happened.<br> <br> Please help me in putting a cap to the service or else I am afraid I might default on the payments. I am generally happy with the quality of the service but this over payment is hurting me heavily.<br> <br> Thanks<br> Dev