if you cant get it, then close your old accounts.

Then a week later open a new one and inform support you have opened a new account because you didnt want the old one and thought you wouldnt need it etc.
Ask them to waive the sign up bonus and they probably will let you away with it, just dont depsoit much cash util you have done it.

Normally the big sites wont argue about it.

Edit: if you try and do the sign up bonuses twice, without informing support, dont complain when they rape you later. Playing 3/6 it shouldnt matter anyways...