What can I do if my English level is lower than the minimum requirements?
The higher up the requirements are imposed, the less flexibility there is for circumventing the policy.

The reason for having such policies may be related to satisfying needs for teaching assistants and for being able to handle the communication needed for taking coursework.

Your best recourse is probably to retake the test, rather than trying to get an exception that could cause problems later on if a new set of policies are put into place.