What state are you in? There are a number of states that actually have laws mandating some form of reimbursement for elemental formulas.
http://www.neocate.com/reimbursement/insurance-coverage-map/
If you do not live in one of those states I would encourage you to keep trying to get the formula covered by your insurance company. It may be an uphill fight but there are some things you can try, like having your doctor write a letter of medical necessity. There is a sample letter and some other great information and support on the Neocate website:
http://www.neocate.com/reimbursement/
http://www.neocate.com/reimbursement/resources/
HTH!!