Idea Cellular — Not able to send sms for porting to 1900

Hello,
I am not satisfied with your Internet Network & coverage.
Hence, I thought to move to Jio...So, I tried to get the MNP code by sending SMS to 1900 for Porting..
But, Whenever I send message to 1900... I get message
"Incorrect request, Please send the request with correct format."
I have tried this numerous time. Every time I get the same message.

Please note that there is nothing wrong in the format that I am using.
PORT mymobileno

Yet, I am getting this message.
I tried reaching out to customer care to resolve this issue.
However, customer care executives are unreachable for solution...they keep giving nonsense / irrelevant solutions: -

1.We will try to fix this from backend.
2. You will get call from backend team within 24 hours. I never got call.
3. I have to change the handset - I tried but no result.

Moreover the Customer care representatives are not available to address the issue, they make silly excuses and are not giving a chance to speak.

Plz help me...
- Saurav