The transaction status problem is becoming common and many are complaining of the same. I would recommend to wait for 1-2 days to let the server traffic slow down. AIIMS Servers are not designed to handle such huge crowd, when opened at same time.

Kindly remain patient and try after 1-2 days. In order to get the refund kindly contact the official numbers and email during office hours of 9am to 5 pm.

https://www.aiims.edu/en/departments-and-centers/central-facilities/79-about-aiims/6815-aiims-exam-section-helpline-numbers-and-email-id.html

The above links have all the numbers and email.