DId you ask why they couldn't fill it, your insurance may require prior authorization or not cover them at all, in which case you would maybe be able to pay cash, I personally have nothing but problems with CVS, I use RiteAid, try a different pharmacy maybe,
I would also contact CVS directly. There is a place on their website to send a complaint. It is probably some overzealous pharmacist, and they can get things resolved for you as they are quite responsive.
You should contact his doctor. The Pharm. can refuse to fill a script if they suspect illegal activity or on the doctors orders or if it is too soon. What is the reason the pharm. told you they wouldn`t fill it?? I feel thee is more to this than what is being told.