Trouble using debit/credit card for online services.

Hi, I'm currently spending some time In Thailand for the next week and a half. Despite calling my bank(United States) to notify them I will be in Thailand during this time, I am unable to purchase anything online, such as making reservations or buying tickets. I can use the various ATMS around the city, however it is frustrating to be unable to make any purchases online. I have attempted to contact my bank to resolve this but they are unable to help me apparently.

Is there a way to circumvent this issue, such as purchasing a prepaid debit card that I can use for online purchases? If so, what stores can I go to to top off a card?