Unable to use savings account

So I need to get new glasses. My scheme will not cover the full account from the optometrist but I have more than enough money in my savings account to cover the full amount. Now I am being told that I need to write a letter to bestmed in order to be able to get access to MY OWN MONEY? Why not just allow the service provider to directly get the funds not covered in my scheme from my savings account?<br> <br> Utterly disappointed in how you handle situations like this.