After policy is effective, can the policy maximum and deductible be changed?
No. Once the policy is in effect, the policy maximum and deductible cannot be changed. So, in order to make changes to the policy maximum or deductible you would have to cancel your current plan and purchase a new plan.
To see details and instructions on how to cancel an existing policy, see: How to Cancel a Policy
Insurance rates are regulated by law. You can't find the same insurance plan for a lower price anywhere else