I'm being charged on an expired contract

Hi Telkom Billing Department

Can you please do Two things for me

1. Cancel the billing amount for *** for Feb 2020 2. Refund me for a portion Jan 2020 for ***

The contract for *** was taken out in 15 Jan 2018 and was cancelled on the 15th Jan 2020 but the invoice for Jan 2020 reflect a full amount for the month even though the contract was cancelled on the 15th Jan already so please amend the invoiced amount and give me my refund

With the *** contract already cancelled in Jan 2020, I should not be receiving a billing amount in Feb 2020. Please correct this in your Feb 2020 invoice and send me the correct invoice showing me a single contract with Telkom.

I spoke to you social media people and they promised to correct the problem but to no surprise this was never corrected.