Do I select different template before send message? If so how can I?

Yes, you can select a different template each time before sending a reminder message.
Log in as the account owner.
From your Shopify admin, go to Apps > Whatsapp Chat Support Share.
Find  from the top and click on it.
Search for the name or user from the list and then select a template from the popup window. After then click one the send action button to send a message.

Do I select different template before send message?