OT prescription law??

Will somebody with a cool head please try to explain pharmacy law to me?
Last week I noticed that my blood pressure medication would run out on
Christmas Day. I thought they would not like to make an emergency trip to
the store so I called in the refill number.
Well. I tried.
The robot that answers their phone said it was to early to refill.
Now. I really like that robot. He asks simple questions, I punch in
the prescription number, the # sign when he gets it right and then I punch
in what day and hour I am likely to appear to hand over my $s and get my
pills.
No problem. Works for me.
Today I tried again. Gave up with reasoning with the robot and had to
speak with a real pharmacist.
I like them too. They know lots. Quite often, they know a heap more
than our fine cardiologists do.
The question is: What is it with filling a prescription too soon? Is
the drug company or the insurance company going to declare bankruptcy if I
mess up their regular schedule? Do they think I'm going to sit outside the
Old Folks Home and peddle my pills to innocent old coots? What?
This baffles me. It's not like I was taking really good stuff. It is
only such a low dose that they don't make one and the smallest has to be
chopped in half.
Anyone understand this? Polly