Tata Docomo — unable to send messages from tata docomo

Address:

Manikonda, Hyderabad, Telangana, 500089

I have a tata docomo prepaid number. Whenever i am sending a message, it is declined and it is shown as "message not sent". I want to port this number to jio, however since i am not able to send messages, i am unable to apply for mobile portability also.. I have recharged this number and i am able to receive messages but i am not able to send messages.. There is no proper customer care of tata docomo whom we can approach.. When approached the customer care center, they are not able to help... Pl check and help