Predictive Dialer API 429s during JMeter load test on US1

Need some help troubleshooting rate limiting issues with the Predictive Dialer API. Running JMeter 5.6 with 20 concurrent threads against POST /api/v2/dialer/calls to validate throughput for a new outbound campaign setup. The environment is US1. The test hits 429 Too Many Requests errors almost immediately after starting the ramp-up phase. The error payload returns a Retry-After header of 60 seconds. I have checked the documentation and it mentions standard rate limits for dialing actions. I am not seeing any specific error logs in the Architect flow itself, just the HTTP 429 response from the API gateway. The goal is to understand if this is a hard limit per tenant or if there is a configuration setting to increase the burst capacity for predictive dialing. I have tried adding a constant timer in JMeter to space out requests but it still triggers the limit. Is there a way to request a temporary increase for load testing purposes or is this a fixed threshold for predictive routing campaigns? The current setup uses a simple flow with no complex data actions, just direct dialing.