No, there is no limit.
A user can have as many contacts as they want. A user manages a shorter list of contacts in My contacts and also has access to all the registered users in their Amazon Chime account. The extended list of users show up when you take actions such as
Visit https://answers.chime.aws/questions/478/how-can-i-manage-my-contacts.html for more details about managing contacts.
View the Amazon Chime User, Administration Guide and API Reference on the AWS Documentation site.
Find more information about the Amazon Chime solution, pricing, customer references, getting started, and other resources.