A company that debits your account for their leisure

I canceled my SIM card with them well in advance however I am still getting billed.... I got bill for this month and I am greeting billed for next month. Please explain why this is happening and when my ticket will be attended to... It is covid and we work too hard for a company like yourselves to go into our accounts and debit when ever you feel like it. Sort this out ASAP please and delete my banking details while you're at it!!!