The Doctor hated to dampen Martha's spirits, but he would do her no favors by hiding the truth. He gently plucked the phone from her fingers and set it back in its place on the console. "No. I'm sorry, Martha, but I can only program a phone to reach across time in one dimension. The walls between realities aren't meant to be breached. It's nearly impossible to manage, now that my people are gone. We're stuck here, either until whatever brought us into this world kicks us out, or until I can sort out which dimension we're in and which way to go to get back to our proper one."
The rest of the things she had told him, he filed away. He'd have to go looking for Jack later, find out when he was from, and then perhaps do the same with Ianto Jones and Gwen Cooper. He needed to know how much of a mess this whole situation was creating. As for his other self ... Well, no need to go looking for that sort of trouble until he had to. He didn't exactly relish the idea of facing the man who would replace him when he died.