Plourde Sand & Gravel

I am a bookkeeper for a long time customer of Plourde Sand and Gravel.
By long time I mean over 30 years.
In the middle of December, I was told that we had a $ 3000.00 credit on our account by them. I requested a refund. It's over a month now and I still have not received the overpayment, which was my fault..
I have called at least 5 times about this, telling them I did not want to leave the money on our account as a credit. They have been playing phone games when I call.
Is this any way to treat a long time customer?
Hopefully we can find another supplier.