A few days ago, a user on this forum asked if it was possible to reverse a bitcoin transaction cause he accidentally sent funds to the wrong address. That's the kind of post these scammers look for. I'm sure he got a couple of messages from people claiming to have a solution to his issue.
Not really a scam but its possible to reverse a transaction if it has not yet been confirmed on the blockchain by using the "replace by fee" aka "RBF" which achieves this by double spending to invalidate the first transaction.
And rule of thumb, if you want help and you do not want to be scammed... keep the conversation in an open space ,unless it gets to a point of dealing with a reputable user and some details aren't meant for all eyes to see!