Way back when, I had a company mobile, which strangely, simply refused to dial a certain w/salers number - not the cell, it was the same anywhere in the county. My own Iphone, seems to have a similar issue, with some numbers. I enter the number, press the green button to get it to dial, then nothing, complete silence. I switched it from internet dialling, to mobile - the same result. Tried dialling my landline, which worked just fine. It's happened three times, in as many weeks, with different numbers. Any ideas why?

