Liars

I am turing 62 in April 2009. I planned for my retirement and part of the plan included approx $800.00 I was to receive from Social Security. I received a yearly letter from SS each year saying I would receive Approx $800.00 a month at age 62. When I applied at the SS Office, they told me it will be reduced to 500.00. My question is, why did SS lie to me by wrtting me and telling me I would get $800.00. then reduce it to $500.00. How can a person possible plan for his or her retirement if it is based on lies? The people at the SS Office blamed Ronald Regean. They told me that he made them lie to me.