Any tips for dealing with telephone cold callers?

[ronnie21]

Had a call this evening to inform me that the Dyson engineer will be calling to service our Dyson cleaner on Thursday.  I asked why, she said it was all part of the contract!!  Told her that ours was broken and could they bring a new one under the terms of the contract?  She said she was sure the engineer would be able to repair the old one, when I told her we had never actually owned a Dyson she rung off!!!  Sadly this was before I had the chance to tell her to f*** off!!!