Update: Minersource contacted me and said that I need to pay another $30 for shipping or get a refund based on a reduced amount of BTC because the exchange rate has changed. They said they don't even have the PSUs in stock despite listing them on their website as "in stock" over a month ago. I filed a complaint with the FTC and I am waiting for a response from Minersource.

Anyone know which payment processing company they use, so I can contact them next?
Minersource uses Bitpay.
I thought this didn't sound like Minersource - and actually
it looks like it was your mistake sir.
The PSU's minersource is selling specifically state "FOR COMPENSATION UNITS ONLY". They are for customers who bought miners from minersource and these are add-ons to that order. Asking for more shipping checks out because they would ship for free with your order, but you don't have an existing order from them, so they won't ship free.
I'm basing this on your previous post.
I didn't place the original order with Minersource! I ordered before minersource was an affiliate and will receive my orders directly from BA. The only reason I ordered the PSUs from them is they listed them as "in stock" and are based in the US.
What do you say bobsag3? Are you going to ship my PSUs or issue a refund?
So. Contacting the FTC seems like overkill, don't you think so? Also they offered you a refund. If you paid what is it, $99, they offered to refund you $99. To pay you back the same amount in BTC they'd have to spend more than you send them to refund them.
Getting the picture?
Maybe they can refund you in store credit?
I'd just accept the fact that there was a miscommunication and pay for the shipping. Perhaps minersource should have more clearly said they were ONLY for compensation units ordered from them but I for one thought that was reasonable to imply.
Update: I don't know if this is new but it clearly says on the product page "No free shipping if not ordered from us."