I am continually harassed by MBD Attorneys for an ...

I am continually harassed by MBD Attorneys for an account of someone I don t know. (Mistaken identity). They also phoned this person (who we don't know) at my work place. Where do they get their numbers from??
I get threatening calls and sms s on a continuous basis. I have phoned their offices and have told them that I am not the person they are trying to trace and don t even know the person and to please remove my number from their system. I have spoken to a consultant and they said that my number would be removed.
But lone and behold, early the next morning I got another SMS of harassment. Can I lay a charge of harassment at the police station and if so, where would this lead too?