Do I need an H1B amendment if middle vendor changed

I work on an EVC model, I will need to change the middle vendor because prime vendor to the client will no longer work with the middle vendor. Do I need to file a H1B amendment? Note that my client is same, location is same, primary vendor to the client is same. My employer says that should not be an issue and no need to file an amendment. I will be planning for an india visit soon and will be using drop box for stamping renewal and do not want to take a chance. An honest response would be appreciated. Thanks!