BSNL 3G card keep disconnecting frequently

Hi,

I have a bsnl 3g data card when I am using it, it works good for few minutes and then there is no data transfer at all and it looks disconnected but actually it is still connected. It works for few moments when connected and works good and then to make it work again, I have to disconnect and then reconnect and then it start working. Then again it works for few minutes. I am not able to find reason. Same data card works very well for other network data card and this data card has worked well with bsnl also in past. I think they have some problem but I am not sure. If there is any solution to this problem then please help.