I don't want a new number, I like this one!

???

Hello folks I've got a brand new mobile phone number and the very first call I've had on it was an automated message from AIC requesting that a person whose name isn't mine call them urgently. It seems they're a debt collection company. I called them gave them the reference and explained that I'm not this person, it's a new number and nothing to do with me, but all that got me was an aggressive response that I must be this person as they have given my number. I refused to give my name as it's none of their business, and I don't want my name associated with someone elses debt and they said they would keep calling unless I did. So I made one up. Bizarre. Anyway if they keep ringing, as I suspect they will, what can I do about it to make them stop?