TI-API: Error when I change request ship date via API

Tool/software:

Hi Team,

I have tried to change request ship date via API, however I have been receiving these errors.

"messages": [
{
"code": "TI-TXT-062",
"type": "ERROR",
"reason": "customerLineItemNumber 1 cannot be changed",
"message": "customerLineItemNumber 1 is in process by TI and cannot be changed. If you are still having issues, contact TI customer support https://support.ti.com/csm"
}
]

Please kindly check and let me know what is the issue here. Thanks!