Replying To [Joyce_lau]:
Do the same as I do.
1. Send them the details and information they asked for.
2. About a week later, send them another email asking if they have received the previous email.
3. About 1 month later, another email, just in case when your 1st email arrived, they might have been away on holidays.
4. If still no reply, forget it, move on to the next customer, who might require more of your time than this last one.