British Council — Why is there no system of retest for students?

Contradicting result-If I am not satisfied with one type, why does a person have to give all exam again? Don’t you have a more efficient system for students can retest without affecting other scores? I have wasted over 100, 000 INR till now over this exam. It does not test my English skills in any way since the results are very contradicting each time! I have got 8.5, 8 & even scores 6.5 in same category.