Express Scripts review: Changes your prescription

I need a cream to help with skin cancer, I have it all over my body from living in Hawaii and other sunny places. The treatment is a cream that comes in 40 gram tubes which must be applied 2 times a day for 4 weeks. My doctor knows that 3 tubes are needed to cover the area to be treated...
My insurance plan says that medicines are supplied for 9o days fills. Express scripts takes it upon their self to change the prescription to 1 tube instead of 3 tubes. 1 tube will not do the job, and you cannot start and stop the treatment waiting for months to get another tube...
WHO's the doctor? Not express scripts. The first time I called them they admitted that it was them who changed the prescription, now they change their story and blame the insurance. But I called the insurance company, we know who did this.