Tata Docomo — tata docomo sim card shows no service

Address:

Lakshmipuram, 2nd Floor, 560008

My tata docomo sim card is showing no service for the past few months. Sometimes network will pop up for a few moment and then dissappear. I have tried restarting the phone but this helps only the moment phone is restarted and there goes same issue. This sim is pretty important since it's link to everything important. So kindly help me with regards to this problem (No service).