I worked in both CS and Public relations for 3 years with BG. I take it you are on a budget plan whereby you pay a set amount each month?
The first thing to remember is that the plan is designed to run over a rolling 12month period, and beleive it or not if supplied with regular reading they DO work extremly well, BUT you need to review it at the right time.
Now, by 1) refusing to give a refund, they may just be saying, "Hold on, we're coming up to the time of year when the biggest bills fall on the mat (Which is actually May/june!) so wait until budget year end.
2) They CANNOT hold onto your money in this manner. Yes the staff are told to try to prevent refunds if at all possible, but go back and insist, under the terms of the arrangemnet you ARE ENTITLED to any over payment back.
I have dealth with this many thousands of times.
I will however say though, that whilst it may seem at this moment you are overpaying, I really would suggest you try to hold on until the plan year end if you can, it really does make a difference, an no it is not designed to benefit BG, it's just the way the calculations are made. What makes it worse is people who build up a credit before christmas (which is actually built into the plan) then want a refund then complain when their payments go up after getting a large winter bill - due to the fact the cash reserve was given back. A good run plan with regualr accurate readings will on average work out for over 90% of people with little or no changes to their payments from one year to a next.
I'm not sticking up for BG here, many of thier staff are poorly trained now and some of thier systems suck.
I was treated appallingly and ended up having a nervous breakdown due to them, (I went from a Public relations manager controlling staff and budget working all over england and having company car etc, to sitting on a phone and having to put my hand up to ask to go to the loo!) but this is a field I know well.
If you want further explanations drop me a PM.
Woody