experienced webdesigner to fix existing e-commerce script

Current website is on prestoshop [login to view URL] has a problem wheres the drop down menu of the item will not log the size therfore when a customer makes a purchase i do not know what size they have ordered. This i return steers many sign up registrations away nd not to complete the checkout. I have trid many web-designer who all come back with disappointment to say that they cannot fix the problem. Therefore right now im looking for someone who is confident for certain this can be fixed. Also it is a matter of urgency if you can give me a timeframe of when you would start and complete. If all elese fails in fixing it posiblity to re-do the entire site. No timewasters please or unreliabe people who fail to deliver. thanks