Add comprehensive tests for calls.py

**Describe the Feature**

Add a complete test suite for the functions defined in calls.py to ensure correctness, reliability and proper error handling. This includes covering synchronous and asynchronous API calls, different response formats and edge cases. This improvement helps prevent regressions and increases confidence in API related changes.

**Considered Alternatives**
- Partial testing of only key functions
- Relying on manual testing

These were not preferred as they leave gaps in coverage and increase the risk of undetected bugs.

**Additional context**
The tests will mock external API calls and focus on validating:

- Response handling
- Error conditions
- Edge cases
- Async behavior