Hi Raghavendra,
If you don't want to use Graph API, the easiest way is to use deep links. For example, try adding a link to the following (using your own email + one of your colleagues)
"MSTeams:/l/chat/0/0?users=user1@domain.com,user2@domain.com"
For more information please refer to https://learn.microsoft.com/en-us/microsoftteams/platform/concepts/build-and-test/deep-links?source=recommendations#protocol-handlers-in-deep-links.