Unauthorized Billing

We renewed out internet contract in August of this year. I kept telling the agent we are not interested in a mobile line as we are with AT&T. We were charged $42 for the taxes on the tablet. I mailed the tablet back and we were refunded $12 and told there is a $30 restock fee. This morning I just noticed we were billed a “final” bill to the debit card for $26.66 to close the mobile line we never wanted