Do you hire off role employees for Hyderabad location

Hi I am Mohd Mehraj from Hyderabad India. One month back I got a call from a company called "iEnergizer" which is located in Noida India. They said that they are hiring for Network Support Engineer for their client and they have received my profile from Naukri.com. So I enquired about the client name and location, they said they will reveal after compitition of few rounds. I have successfully completed 4-5 rounds of interviews and lastly I completed Versant Test. Later they revealed that I have been hired for AT&T Hyderabad location as Support Engineer L2 on their payroll(not payroll of AT&T). I have got the offer letter as well in last week of January 2020. I just wanted to know that whether AT&T has given authority to iEnergizer to hire employees and deploy in AT&T on their payroll. Kindly answer my query.