Talk to Dermatologist on Medical Certificate For Illness

I had a fever few days ago, while I was also taking antibiotics and antifungal medicine due to eczema. on 30th January 2026, I had my exam of English language (IELTS) but I was unable to give and travel to Islamabad. Now organisation is asking for medical certificate for my exam rescheduling, although I have doctor's prescription with me dated 2-3 days earlier than exam date. Now, I want to get medical certificate for myself but I couldn't get from the doctor I visited for my checkup of skin infection.

Can any doctor help me or guide me how I can get the medical certificate mentioning that I was unable to take exam of 30 January due to illness, as certificate should mention the exam date along with doctor sign stamp and registration number.