We connect to your existing bank account and make the payments automatically to build credit. Traditional debit cards do not do this.
The only novel thing here is you are deceiving the processing networks by claiming your debit card is a credit card. My credit union tried to do the same thing many years ago (as a way to build credit for students) and it eventually got caught by the processing networks and recategorized. Within a month or two it dropped off everyone's credit reports and they were back to square one.
We are an official Visa partner and deal directly with credit bureaus.