Did you know that there are more non-native speakers of English than native English speakers? Some students say: "I only want to learn American English" or "I only want to listen to British English". This is not good thinking .
IELTS, TOEFL & TOEIC use a variety of different English accents: British, USA, Canadian, Australian, New Zealand and South African. IELTS also has used non-native English speakers in the test. For example, you may need to listen to English being spoken by a German or Japanese speaker as part of your test. So you must get used to a variety of English accents!
The point is: ALL accents used in the test are clear and understandable and you must learn to understand them all.