Telkom not acting on cancellation request

we cancelled the Telkom ADLS line which has not been in use for the last 4 years since we went over to LTE, via email in November 2019 and follow up emails was sent in December 2019 and January 2020 as it was not acted on. I just got an account that they request me to pay for three months which now includes February ?? …. honestly !!!!!! what can one do for Telkom to act on a simple instruction ???