Eskom bill

We have been receiving and paying Eskom monthly bills for our 74 year old mother who is staying alone in Saul****rt village. To our surprise, her bill for December 2020 amounts to R5,418.90. My sister contacted Eskom customer service today, the 19th January 2021 to lodge a query. The rude consultant advised that the meter readers took the readings from March 2019 until 22 December 2020, and we MUST PAY, because even if we lodge a query, it won’t change anything. The reference number is ***