CSD connection on AirPrime WP7502

We would like use WP7502 in low speed csd connection mode.
But command ATD+791388169xx immediately returns NO CARRIER.
+CEER: Client rejected incoming call
We use those sim cards on other modems - all work right.
what could be the problem?

Best regards

WP7502 does not support CSD, none of the QC platforms do, they stopped support for it years ago.