After you file

step one; to change your dependent status, the only way to do it is via the explanation Part III.

Step two; to claim the rebate you have to put the amount you did not get on 1040-X line 15 other.

enter "rebate credit" in the space provided..

 

If you did not do these things, you can submit amendment No 2. and try again.

BUT if someone did claim you then there is a conflict and that has to be resolved by the IRS.