How can I get my spousal support payment amended?

The answer to your question, in short, is that there really is no answer.  You are seeking to modify a spousal support award, I presume, which was issued in teh context of a divorce case.  If this is accurate, you have to show an unforeseeable change in circumstances which would justify the change.  Your daughter going to college is not necessarily "unforeseeable" but there could be other reasons to justify a change.  Two real issues are how much is your annual income and how long were you directed to pay the support?  Please advise.