Cell C double debiting and failing to refund me

Cell C has debited me an amount of R1187 on the 18th of December 2021, R1677 and last one was om the 25th December 2021 was R489. Now they say I must send them the proof of the debits from my bank statement. They have been saying this for the past 7 days and still have not been refunded my R1677.00. I am an existing customer there and they should refund me the money as soon as I said there was an error made, but they keep on asking me for the bank statement.