Getting the interview date in Almaty U.S Consulate, Kazakhstan

[Bunny Gurl 9]

My mom was initially scheduled her interview on June 18th this year, but we couldn't go, because it's too hot for her there in the summer, she is an elderly and not a well person. I called the embassy in Almaty, and they told me, after the scheduled date passes, I'll be able to open the scheduling page an pick my own date.
I've been trying to do that since June 18th. So far there were only 2 available dates - on July 11 and 18th. Neither of those suit us. We'd prefer September the 27th. They don't schedule it for you over the phone. I also tried to write an email to the office, which scheduled the interview initially, they are saying, they can't help and just refer me back to the scheduling page.

My concern is if there is any deadline after the case has been approved, for obtaining the interview date.
Also, does anyone have a recent experience scheduling the interview for IR-5, like we are trying to do now?
Can you give any tips to succeed?