Contract cancellation disput

Cellc at it again still forcing me to pay for expired contract, contract expired 10 December 2024 . i sent 30 days cancellation notice email that server as a proof with no response ,they failed me ,unprofessional service received only to be cancelled 10 January2025 now they said I should have called to inform them however I have followed the procedure requested by cellc customer service agent, today got a call from VVM Debt collectors that I owe January 2025 amount for benefits i told to F....., cellc has unprofessional and incompetence customer service agent . I have countless emails sent to cellc with references no response . ( we have received your email regarding your cancellation .) They used my signature number as number in question which was wrong number, will use the email as proof of cancellation when escalates the matter .I am tired with cellc's harassment and treatment they treat me like ******* or is cus they are a big company