jecasc - 10:06 am on Jun 11, 2010 (gmt 0)
Check your contract, if there is nothing in it about them having the right to hold the funds, then change your provider and threaten legal action if they withold the funds in violation of your contract with them. However if you agreed that they can withold money at their own discretion, you are probably out of luck.
I use Paypal for credit card payments and withdraw all money on my Paypal account every day.
It might also be a good idea to check out alternative payment options. I am glad here in Europe customers are not hooked on credit cards. Credit card payments only are 1/3 of our orders, the rest are direct debit, bank-transfer and cash on delivery. However I have heard the banking system in the US is so rotten, people still even use cheques.