Hi, unfortunately yes, you have to take IELTS no other proof of english is accepted
I dont understand why but even native speakers have to take the test.
Let me give a detail of how IELTS Points are awarded
Listening:
Band Score 5.0 to 7.5 (1 point)
Band Score 8.0 to 9.0 (2 point)
Speaking
Band Score 5.0 to 6.5 (1 point)
Band Score 7.0 to 9.0 (2 point)
Reading
Band Score 4.0 to 9.0 (1 point)
Writing
Band Score 5.0 to 9.0 (1 point)
Goog luck! Oh! one more detail it has to be IELTS General, academic version is not accepted