Do players have a choice in whether they get transferred by a club?

Yes and no.

Since the Bosman rulling the player calls the shots and the agent does what the player tells him.

Yes, however a club and player’s agent can overrule what the player wants if they think it’s better for the club and player.

If it's in the players contract then yes the club can sell you whenever they want to whoever! Can you put such terms into the contract I don't know but you can't force someone to go when they don't want to. Diego Costa could have left but wanted to wait for Atletico Madrid's player registration ban to be lifted. You can't make the player leave but you can not play the guy and hopes he leaves. And like any other job you can sack the player if necessary.

Yes they do lol but if a club wants u at wants to sell you for no reason why should u be committed to them? Rather go to Italy in the sun and get wasted with italian chicks

no