I got ITIN for my spouse for 2008 tax return while my spouse was still living outside the u.s, but three weeks along my spouse got an immigrant visa and relocate to u.s, I applied and got SSN for my spouse, when I put the ssn into my 2008 tax return I found out that my tax payment was reduced I was awarded some credits, but already paid all the money own, can fill an amended with my spouse ssn and got back the money,(credit) already paid.

Sorry, but, at the time, the ITIN was the valid federal tax ID number for your spouse.

That being the case, the original return with the ITIN was the correct return to file. Amending the return using the SSN, which was valid only for 2009, would be considered tax fraud.