Originally Posted by The_Judge_:
“Martha has it as well I believe.
I didn't think the TARDIS has two phone numbers, may be wrong though ....”
It definitely does.
When Clara calls the outside phone in The Bells of Saint John, he says, "That is not supposed to happen." He's referring specifically to the outside phone, not the inside one, people ring the inside one all the time. He's not surprised someone's got the TARDIS' number, he's surprised someone's got
that TARDIS number.
The one on the outside is a different device - he patched the interior one through to it, but only temporarily: "Remind me I've got to patch the telephone back through the console unit. This is getting ridiculous." He's got two phones, one of them had a redirect for a bit. Not visually clear, but it's relatively consistent.
(And Martha has her own phone number! She gave the Doctor her old mobile phone, it's an 07 number. Which, again, he's presumably redirecting as it shows up in The Day of the Doctor.)