Green Dot provides the walmart prepaid cards. Here are the stipulations (which can be found at https://www.greendotonline.com/contents/products.aspx):
Limits Card balance (with cash load) $2,500
Minimum Initial Load $10, varies by retailer
Card balance (with direct deposit) $10,000
Daily cash load limit $2,500
Daily direct deposit load limit $10,000
Daily ATM withdrawal limit $400
Daily bank teller cash withdrawal limit $400
Daily spend limit (includes all outgoing transaction activities, such as purchases, ATM transactions, etc.) $2,500
If you were trying to pay the person by ATM or Teller it wont let you as you can see. So it really depends on how you were attempting to recieve your money. If you did something else with the cars, like make a purchase, they can hold double the amount of the purchase to verify that the funds are available, thats called a Authorization Hold. Although I cannot find it on the site, Green Dot may also have a turn around time before you can utilize funds.