GfK NOP (gfknop.com)

I've just had a call from a company calling themselves GFK NOP (gfknop.com), telling me they were conducting a survey on how satisfied people are with their banks or some rubbish like that. The call came from 0207890905.Now here's the problem - I'm ex-directory and TPS - which means they shouldn't have my number. When quizzed as to where they got it, I was told they obtained it using "standard