I contacted Bangalla and received a prompt reply and explanation on this matter. Karin has explained that with your Gold membership, you will not see the 5% discount at check out. Rather the gold discount program works by automatically reducing all the prices by 5%. The overall price at checkout is already discounted.The prices can be compared without being logged in and also when logged into their account.
Concerning the FBA, Karin stated that she did notify you that there would be additional charges before the order went into process. She offered to credit you for the order before the item was shipped and she further suggested a different product that did not require shipping at all. I believe you chose to continue with the order, and therefore you got charged for the shipping fee.
Bangalla has already confirmed with you via email that they will cancel your Gold membership program per your request after this month. No further charges will be billed to your account. And because you were unsatisfied with the service, they have made an exception and your shipping fee will be refunded.
Does this help clarify the matter on their membership program and the shipping charges?