Whataboutism is for excusing egregiously bad behavior. A politician lies and lies and lies about almost everything, big and small, and when confronted, he points to how his opponent once exaggerated an accomplishment. But selling data isn't unusual. Selling data is the norm. I get a "free" service, and in exchange, I know my data will be sold. I can pay for Slack if I want, or set up my own IRC server.
If I'm going 70 MPH in a 65 MPH zone and the cop pulls me over for speeding, and then I point out that actually traffic was moving at 75 MPH and one guy just zoomed by at 90 MPH so what about them, it's not whataboutism. It's a legitimate argument of unfair application of a criticism.
I'd say you're engaging in the name-a-fallacy fallacy, where a person doesn't understand the argument or the fallacy they accuse the other of using.