The difference between SSI and SSDI:
SSDI is based upon your lifetime earnings...SSI, on the other hand, is only available to those who have not had a minimum level of lifetime earnings, judged by amounts paid into Social Security.
In other words...if you have not had a minimum of earnings, on the books, and so, a minimum of such paid into the Social Security system...you are ineligible for SSDI, and will only be considered for SSI.
SSI payments are considerably less than those of SSDI, however, qualifying for SSI qualifies one for medicaid coverage, nonetheless.
As far as advice as to how to conduct your phone interview...I can only say to "watch your p's and q's"...ie, say nothing that is inconsistent with your application. It wouldn't hurt to have a copy of the application in front of you during the interview.
It's likely that the official responsible for your interview will ask "trick questions" in attempt to determine whether your claim is legitimate. It's important not to minimize your disability or symptoms, even in making such seemingly innocent remarks as "well, I get along...I do my best and function as well as possible" etc. Remember, your qualification for disability is based upon the premise that you DO NOT FUNCTION, so to speak. It's often a matter of human nature to minimize one's difficulties and inability...however, this is not the time to do so.
However, going overboard is also a red flag for the interviewing official. To make claims along the lines of "I cannot feed myself, clothe myself, etc.", unless a physical disability is involved....also make it more likely that your application will be flagged.
Try to be casual, and matter of fact. Offer no more detail than is requested, and answer questions as briefly as possible. Extensive elaboration is also seen as a sign of dishonesty.
Good luck.
