The tower can not grant you permission!
They can only acknowledge your presence and help you and other aircraft avoid each other.
Think of them more like the police officer guarding restricted area. Thye can not give you permission to enter. You must have "airspace authorization" granted by the FAA via their web portal, prior to to you flight. You submit your request on their website and receive authorization a few day later. Once you have this you can submit it to DJI and they will lift the NFZ. This has been my experience. As a part 107 UAS pilot you should know this information. Or hire a real commercial pilot to do this part of your $23,000 job!
I do work inside class C airspace fairly regularly and have had no issue when I go through the proper protocols. Best of luck to you.