Set Spend Limit *****ulently set to R1500! Please assist!

I took a contract phone via iStore and was told that they do not have a top-up plan however I need to contact Telkom to ensure that the line is managed spend limit set to zero. I then called Telkom and was advised that the spend limit is set to zero and I can also check same on the app and I did and it was updated correctly. Today I went on the app to check my 1st invoice and I see the spend limit is set to R1500 and I’ve been trying to get through to someone to get this fixed but the call centre agents keep hanging up on me. Please set my spend limit to a zero permanently. I cannot afford to pay more than what I am already paying for the phone and I am getting enough benefit from the plan I am on.