Tata Docomo — unable to send sms to 1900 from tata docomo

Unable to send sms on 1900. I have sufficient balance and nothing is due on me. I have prepaid no.
While customer care shows busy and on my docomo app it shows number barred for non payment. I wonder how it is possible.
Every thing is ok as calling and sending sms on other numbers. I tried to call costomer care but not resolved.
Kindly resolve it as asoon as possible