I get this a lot. I had one the other day which phoned me 3 times and hung up every time, I tried to return the call but it said number not recognised, I then complained to 'someone' (can't remember name of company) but they couldn't trace them and so just offered to put a blocker for the number on my phone but I said I wouldn't bother. It just makes me so dam angry though, to the point of wanting to rip whoever is calling me head off their shoulders and crapping down their neck.