Locke never was in the army or anything like that, so i think they guy on the phone was a friend talking to him about the wargame he used to play online and he had to go because he was at work, and that refers also to his manager asking him the same question you have asked and, why people call him the colonel.

As for claire i think it's just because her mum was pregnant when she was young by Christian shepard and she didn't want claire to make the same mistake's she did.