3G connection problem

[Aunto Afrad]

I am using htc one v. In few days ago, I could use 3G service with this phone with my simcard. Now, 3G is not working in this device. I can use 3G by using another simcard inserting in this handset as well as I can use 3G with my simcard with another device or modem. But I cant use 3G with my simcard & handset together.

I did contact both of the individual customer service but none could help me.
It would be my pleasure if anyone could help me by giving me the solution. Thanks in advance.