Beware what you been sold

I was sold a contract with false pretences of the cost. The first encounters to resolve were quick as they acknowledged their fault. Once the device was returned I was hit with a 12K cancellation bill which I was told on the call as it was not my fault there would be no fee and all charges of billed months would be reimbursed. I have been mailing for weeks to customer service and no reply about my refund. I have no device no contract and an exorbitant bill to pay with a company that seems to be ghosting me.