I am receiving text messages from an unknown no. at odd times. I called up the customer care to solve the issue. But they said they don't provide any facility to block incoming messages from a particular no. I don't want to change my no. but I am really tired of receiving these messages. Please help me if there is any way by which I can block these incoming messages from this particular mobile no. I am using Nokia hand set and didn't find any option for this. Please help.

Not possible to block incoming SMS at all, I'm afraid.
If these messages are causing your distress then your service provider CAN do something about them.

Well I know with Sprint you ARE able to block specific numbers from TEXTING. You can also call yout tech support team and they can do the block. It is called BMG. It's free of service, and you can also block any txt msg's from coming in or out.

What exactly is this Sprint? And how its been used?

Sorry Sprint is a cell phone provider. What company are you with?

I am having airtel connection and Nokia hand set.

Have you at a minimum texted or called the person sending you these messages and tell them they have the wrong number?

He is not having the wrong no. and I knew that these messages are for me only bcoz he mentioned my name in one of his messages once, but I don't know who this person is. The time he mentioned my name I replied asking him who he is to which he didn't say anything and he keeps on messaging me after that.
He is obviously not a friend because I am in touch with all my friends and not even a lover because I had only one man in my life and I know all about him.
I don't know how to solve this.

Contact the police?

I cant, the family from which I belong doesn't allow me to go to police.