Unauthorised debits

I recieved a call from their agents and i had to recieve a second call from them and an sms to authenticate debit orders from my account, i never recieved the 2nd call, i did recieve the Sms but never authenticated. Now 1Life is debiting my account, with an authorisation from who? I want a reversal of the debit order and cancellation of that unauthorised debit mandate.