JuJu Smith-Schuster says Antonio Brown is giving him the crazy ex treatment -- claiming AB has BLOCKED him from ALL digital platforms ... leaving him no way to make contact with his old Steelers teammate.
The 2 NFL stars had butted heads after AB was traded to the Raiders in 2019 ... with both sides taking shots over social media.
AB had called JuJu a "bum" and mocked his name -- calling him, "Boo Boo Shoester."
JuJu fired back saying, "Crazy how big that ego got to be to take shots at people who show you love!