Is the solution below answer your question?
Click on

on your
very first post(the one where all your item are being listed) in that topic. Edit the Topic Title and Topic Description as you want(You can edit hundreds and gazillions of time if you wants too either).

Editing the Topic Title and Topic Description won't bring your topic to the front page of the forum. You can however use

to BUMP up your thread and it will be listed/jump to the front page(BUMP button only applicable in Trade Zones).
Use the

if you wants to reply to all your customer in 1 shot(applicable up to 10 post if I not mistaken). You can also use

if you want to reply to a particular post
As for this
http://forum.lowyat.net/index.php?showtopi...post&p=14621373 , it will merge all your continuous subsequent post together rather than listing it as single post.Post merging would not bring your thread/topic to the first page listing as well. You will need to follow what vikingw2k have posted to separate it.
Also, you might need to read up Trade Zone rules and regulation, do's and don't
HERE ,
HERE and
HEREthks a lot your info..really appreciate it..