It's a good decision that you plan to build a chat app for your business. Developing a chat app for your small business has various advantages. You can always stay connected with your team as well as clients.
If you are good at coding you can create your own chat app, but i can assure you it is a time consuming process.
If you do not have the resources to build your own chat app, you can choose an ready made instant messaging such as Apphitect IM Solution (www.apphitect.ae/instant-messaging-solution.php) to build a chat app that fit's your requirements