You can surf to Telus.com, then Mobility, then choose 'Travel' then select Barbados from the drop down list initially populated with USA. There is an Easy Roam option and a package of minutes, texts and data.
EDIT: There is a Business Roaming options link near the upper right hand side of the above linked page.
Yes exactly. Corporate is it's own world and each individual corporate account has it's own rules and plans. You need to call in and find out what is associated with your corporate plan. Corporate is only open Monday-Friday 8am-6pm your local time. 1-866-848-3587. You can email them as well at firstname.lastname@example.org but it usually takes 3 business days for a reply.
You can see the available options by going online to the Business section of the website, though. You'll still have to call in to make a change.