API Queries/Requests/Calls in SaaS - What is the correct label/text?

Consider calling them API invocations.

invocation noun 3 (Computing) Cause (a procedure) to be carried out. ‘Can I use a Java application instead of a JSP (JavaServer Page) to invoke a servlet on an application server?’ - Lexico

Here are a couple of examples from the SaaS world (emphasis, mine):

• API Gateway resource policies are JSON policy documents that you attach to an API to control whether a specified principal (typically, an IAM user or role) can invoke the API. - Chris Munns, AWS Compute Blog, Control access to your APIs using Amazon API Gateway resource policies

• The Open API is published as REST APIs, and can be invoked by any REST client. - apppulse-help.saas.hpe.com, How to Use the Open API