Poor Customer Service

I took out new 24 months cellphone contract with Telkom for R1649.00 monthly, which commenced in April 2022. I paid R1780 in May which I am okay with. I received a bill for R39900 for June 2022. I called to query why such a big amount and the response I got was I must just pay or my account will be suspended. When I assessed the bill, the put the full price of the device I purchased contract. If I could afford to buy the device cash, why would I take out a contract?