Your initial question deposit (typically $5) is separate from your membership fee. If you already entered your credit card information and if your Expert has responded to you, then your deposit has been processed. Your deposit remains in your JustAnswer account until you give your Expert a positive rating. You will be charged for the membership at the end of the free trial period.
Please note, the membership plan is optional and you can still pay to receive an answer to one question, without enrolling into a membership.