" he then went on to list them, on my desk top, I could see there were lots of trojans and errors"
That sounds like access to the PC rather than a mere phone call to me.
If you allowed them to control your PC you need to remove any possible nasties they may have left and change and passwords etc, you may have stored on your PC that they may have looked at. If, on the other hand, it was just an unfortunate phrasing of your question and it was just a phone call, feel good that you have learnt to ignore them in future. Do not buy or pay anything or pass over any bank details.