Had an interesting experience four or five years ago. Telephone calls claiming to be from my bank, but sounding more likes a Dalek than a human being. After this had been going on for several days, I phoned my bank to let them know what was going on. Turned out the bloody calls were GENUINE - and because I had just hung up on them they had blocked my credit card!! Thankfully, I hardly even use that particular card, so it wasn't a problem, but when I pointed out that it would be helpful if the calls didn't sound so 'spam', they couldn't come up with a solution - so I told them under no circumstances to phone me again, but to write or E-mail
Mike