Tata Docomo — Sim card not detecting

Address:

Kolkata, West Bengal

Since last 2 months, sometimes my phone can not detect the sim at all. It goes off for several minutes (sometime more than 1 hours) and then come back. I tried with different handset to see if it is handset issue or not. But it seems the problem is with either network or sim. It is happening very frequently. Suggest me what should I do. I have tried restarting mobile, sim on/off setting, different hand-set everything, but nothing seemed to work for me. Its terrible especially when I am expecting important calls or to get OTP for important transaction. Help appreciated. My Number: [protected], I am using this since last 3 years.