Was this the one that came from Peru? My guess is that it was picked while still absurdly unripe. I've encountered this with Avocados here, but not with Mango. My wife actually just bought a batch of Kent and Edward at the market. I'm sure they're grown on the coast (not locally). I guess if I encounter a chewy one I'll know it's the Kent.
So, you got ripped off by Peru even though you're thousands of miles away!? Pretty impressive. If you want, maybe I can seek reparations for you.
Or certainly you're not the only one, maybe we can get Publix involved and finance a class action suit against the growers. I have access to local lawyers here on the ground. The lawyer will probably require a 100/0 split (100% of the payment for the lawyer and zero percent for us) which is the traditional legal way of doing things in Peru.