Exactly what happened to me after my first couple of vials. They refused to fill the prescription as it was written (for a 10 ml vial) -- and that was before they checked with my insurance.
And don't get me started on what it's like to try to get syringes out of CVS. If your insurance covers them, great. Mine doesn't (which makes no sense), and at first they charged me the price they bill the insurance company: around $1 each. Then one of the techs told me that if I buy them over the counter (which you're allowed to do in my state if you have an Rx for something which has to be unjected), the cost would be $0.25 each. That worked for a couple of visits, and then they went back to wanting to charge me the higher price. The woman I was dealing with (who was the pharmacist on duty!) first said they couldn't do that, then she looked it up and found she could, but tried to sell me the wrong size syringe (which would have cost more), claiming they were out of the 1 ml ones. I
very politely told her that I couldn't use those because I was on a small dose and couldn't draw it up accurately with a 3 ml syringe. Then she yelled at me: "I'M TRYING TO HELP YOU HERE!!"
Finally, she went back and looked again, and "found" the 1 ml syringes I needed.
Yes, unprofessional. I thanked her for her help and I never went back there.
Now I buy them online. Allegro Medical has them for around $40 for a box of 100, and it's well worth it -- they ship super fast, too.