Telkom debiting more than they should

I paid off my telkom bill in December 2020 for my cellphone contract which was settled. I only have a router with Telkom which the monthly installment is R367 per month. Now, January 2021 they wanna debit my account with R2330.08. Now when I try to call them to sort this matter out,there’s no answer or the call keeps on getting cut. If this money gets debited, my bank account will go over budget and o will not have enough for the rest of the month for my living needs. Can someone please help before this Money is wrongfully debited from my account?