How to withdraw from SSI only?

I filed for disability in August 2022, was denied initially and then got an attorney. Denied again before I had a determination hearing in front of the judge last November and was approved in December for SSDI. I was told I needed to complete an interview for SSI that would be mid January, and during that interview the SSA worker conducting it made me think that if I chose to withdraw at the time then I wouldn’t get my backpay for SSDI so I went through with the interview.

Two weeks later I got a letter stating that I wasn’t approved for current SSI because of what my monthly SSDI payment is, but I had backpay due to me. Of course that made me think I wasn’t on SSI, especially because online account says SSI is suspended. Got my backpay in March for SSDI and then a week later got the first installment for backpay from SSI.

This whole time I’ve been separated, but just recently decided to work things out and move back in with my spouse. When I called to update my address, I was told that I needed to send in all of my spouse’s paystubs and bank statements etc. She told me SSI needed it, which then confused me because I didn’t think I was on SSI? There’s no way I’d apply for it now because I know for a fact my spouse’s income puts us way above the limit, so my question is now this—

How exactly do I voluntarily withdraw from SSI and not the SSDI? From my understanding, SSDI goes off of my work history and not income-based? Like I said, I was under the impression that I wasn’t on SSI. They said I wasn’t approved, the website says it’s suspended, and the woman was adamant that I have Medicaid and not Medicare. Nothing Medicaid has ever been sent to me, but I have a Medicare card and $185 gets taken out of my disability for the premium so I’m confused.

Any and all help is appreciated.